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Technology.

8 September 2021

Best Sim-only deals: Sky, Plusnet, ID Mobile, Giffgaff and more

Browse our pick of the best Sim-only deals for low, medium and high data users, including 5G Sim deals that won't tie you down
HY
Hamse Yusuf
Mobile phone network report 439291

Deals updated: 2 September 2021

Finding the right Sim-only deal can seem daunting – with a range of data limits to choose from, and some tying you down for as much as 24 months, you’ll need to make sure you choose a package that best serves your needs. 

We regularly scour the market to pick what we believe to be great value Sim-only deals across low, medium and high-data packages.

Find out how to get started, browse some great deals, and decide what other considerations you need to take into account.

See where your provider ranks in the best and worst UK mobile networks for 2021 based on our in-depth customer survey.

How much mobile data do I need?

With most packages now coming with unlimited data and minutes, the main factor driving the price of Sim-only deals is mobile data. In terms of how much data you need, consider how often you use your phone outside your home or place of work (which are both places where you're likely to connect to a wi-fi network). 

Also, it's important to note the types of activities you do on your phone. If you only use mobile data for light browsing you needn't pay a lot, but if you like to stream on-demand video on your commute, you'll need a bigger bundle. That's why we've split the best deals into low, medium and high data. We've also included 5G data deals – bear in mind the fast speeds of 5G may mean you use more than you expect.

Best 5G Sim-only deals

These deals allow you to access lightning-fast 5G speeds – provided you live in an area with good 5G coverage and own a 5G phone. All deals have unlimited minutes and texts.

O2

  • Data Allowance: 20GB
  • Contract Length: 12 months
  • Network signal: O2
  • Price: £10 a month 

If you go through Which? Switch, you can currently get 20GB 5G data for just £10, £8 less than if you go direct to O2.

New O2 customers also get three free months of one popular subscription service of their choice with options including Prime Video, Amazon Music Unlimited and Disney+.. 

Check out O2's Sim-only deals and read our O2 mobile review to see how it fares in our survey.

Three

  • Data Allowance: Unlimited
  • Contract Length: 12 months
  • Network signal: Three
  • Price: £16 a month 

Three is well known for offering competitive high-data sim deals and this Which? Switch deal is one example.

By using Which? Switch Mobile, you can currently get a deal with unlimited 5G data for 25% less than if you go through Three directly (where the same deal costs £20) 

You'll also get a personal hotspot allowance and access to Three's flagship roaming package, Go Roam which allows you to use data and call/text UK numbers at no extra cost from 71 international destinations. 

Check out Three's Sim-only deals and read our Three mobile reviewto see how it fares in our survey.

Best low data Sim-only deals

These deals have an allowance of up to 4GB and will be suitable for people who mainly use their phone through a wi-fi network, or don't use the internet often. This amount of data should be plenty for browsing, light social media use or instant messaging on services such as Facebook, Instagram or WhatsApp. All deals have unlimited minutes and texts.

Lebara Mobile 

  • Data Allowance: 4GB
  • Contract Length: 1 month rolling
  • Network signal: Vodafone
  • Price: £5.99 a month 

A new entrant into our mobile network satisfaction surveys, Lebara Mobile has pivoted from being a Sim provider for international calls to a low-cost Sim-only provider.

Lebara is currently offering the first month for half price on most of its packages, meaning you can get 4GB data for just £2.99. Cost is not everything, however,  - our reviews will let you know if Lebara Mobile customers think the service is as attractive as the price.

Check out Lebara Mobile's Sim-only deals and read our Lebara Mobile review to see how it fares in our survey.

Smarty

  • Data Allowance: 4GB
  • Contract Length: 1 month rolling 
  • Network signal: Three
  • Price: £6 a month

Smarty is currently offering 4GB for £6 a month on a rolling contract, which is a great deal for most mobile phone users.

As a low-cost mobile network, there are not a lot of extra benefits with Smarty although tethering is unrestricted and speed caps do not apply.

Check out Smarty's Sim-only deals and read our Smarty review 

Best medium data Sim-only deals

These deals have an allowance of between 4GB and 10GB and are suitable for people who often use their phone when out and about, whether that be for social media, music streaming or internet-based voice/video calls. All deals have unlimited minutes and texts.

iD Mobile

  • Data Allowance: 10GB
  • Contract Length: 1 month rolling
  • Network signal: Three
  • Price: £10 a month 

iD Mobile is well known for offering cheap no-frills sim-only deals and this deal is no exception.

Currently, you can get 10GB of 5G-ready (which reverts to 4G if not being used on a 5G device) data for £10 a month on a rolling contract.

You'll also get up to five months of access to Apple Music, Apple Arcade and Apple News+ for free when you sign up.

Check out iD Mobile's Sim-only deals and read our ID mobile review to see how it fares in our survey.

Tesco Mobile 

  • Data Allowance: 10GB
  • Contract Length: 12 months
  • Network signal: O2
  • Price: £10 a month 

Tesco Mobile is a well established mobile network that has consistently got high reviews from customers, and this deal is definitely worth checking out.

With an O2 signal, you should expect good coverage, but check out our mobile phone coverage map to see how it looks where you live.

Tesco Mobile also promises not to increase the cost mid-contract, an increasingly popular trend amongst other providers. 

Check out Tesco Mobile's Sim-only deals and read our Tesco Mobile review to find out how it fared in our regular survey.

Best high data Sim-only deals

These deals have an allowance of 10GB and above and are suitable for people who use their phone a lot when out and about, whether to stream high quality video/music on a commute or for creating a wi-fi hotspot for a laptop or other internet devices (if the network provider allows). All deals have unlimited minutes and texts.

Three

  • Data Allowance: 30GB
  • Contract Length: 12 months
  • Network signal: Three
  • Price: £10 a month 

Three makes another appearance with a very competitive high-data Sim deal – 30GB of 5G-ready data for just £10 a month.

By using Which? Switch Mobile, you can get this deal for 50% less than if you go to Three directly (where it costs £20 for the same deal.) 

As with all Three deals, you also get a personal hotspot allowance and its flagship roaming package, Go Roam (which allows you to use data as well as call and text UK numbers), at no extra cost from 71 destinations. 

Check out Three's Sim-only deals and read our Three mobile review to see how it fares in our survey.

Giffgaff 

  • Data Allowance: 100GB
  • Contract Length: 1 month rolling
  • Network signal: O2
  • Price: £20 a month 

One of Giffgaff's 'Golden Goodybag' sim-only deals, this package offers 100GB of 5G-ready data for £20, which is a serious upgrade on the original 80GB of 4G data.

It should be noted that Giffgaff's deals also allow tethering, making this package a viable option if you regularly need to use a hotspot.

Check out Giffgaff's Sim-only deals and read our Giffgaff mobile review to see how it fares in our survey.


Black Friday Sim-only deals

Sim-only deals tend to trickle in from providers in the lead-up to Black Friday, just like with many other products. They're traditionally no-fuss affairs, usually increasing the data allowance or reducing the price.

Other incentives, like three months free with a streaming service of your choice on O2, are often available year-round, so don't get sucked in just because something is labelled as a 'Black Friday special'. Similarly, don't be seduced by a high-data allowance if you won't use it.

It's always a good time to search around for a good Sim-only deal, but that's especially true if you're out of contract. You can compare Sim-only deals today at Which? Switch.

Best mobiles

How to get the best deal on a new mobile contract 

There are a range of things to consider when shopping for a new Sim-only deal.

Work out if you’ll benefit from promotions

You’ll need to decide whether you prefer to be on a rolling monthly plan that offers the flexibility of changing at any time, or tying yourself down to a contract period – typically 12 or 18 months. Usually, longer contracts represent better deals. Providers might offer money off the usual monthly fee as part of a promotion, or a data boost for the same price. 

You might also see streaming services added in at no extra cost – in the past, Vodafone has offered a choice of Amazon Prime Video, Spotify, NOW TV and Sky Sports Mobile with its Entertainment bundles. Compare and contrast though – if you won’t use the extra data, or the streaming service, you may still be better off with a rolling monthly Sim, if you can get it at a good price. 

Find out How to keep track of your mobile data and minutes to help work out how much data you really need.

Are you better off with a phone on contract?

There are also a lot of great contract deals, so if you’re in the market for a new phone, it’s worth looking at these as well. If you can afford to purchase a handset outright and get a Sim-only deal, it’s often cheaper in the long run, but this isn’t always the case. 

Use our mobile phone contract calculator to compare deals when you see them and read our guide on the best mobile phone deals.

How good will network reception be?

Signal is another consideration. If you know that a particular network is good for your area, you may want to stick with it, but move to a different provider. Or if it isn't, it could be time to move. 

Here are the core networks the virtual providers use:

  • O2 - Giffgaff, Sky Mobile, and Tesco Mobile
  • Vodafone - Virgin Mobile and VOXI
  • EE - Asda Mobile, BT, Plusnet, Utility Warehouse
  • Three - ID and Smarty

Do you need 5G?

As the new super-fast standard, you'll probably be itching to try out 5G if you have a compatible phone. 

For more information, read our guide to what is 5G and where can I get 5G in the UK? 

Or look at our mobile network coverage map can help you work out if it's in your area. 

You can also browse our 5G-compatible phone reviews, and if you don't already own one – you can now find models for less than £300.

Should you stay with your mobile provider or switch?

If you’ve found a deal that you like, but you’re otherwise happy with your provider, you might be a bit reluctant to switch. 

You could try haggling with your mobile provider to see if they can match or better the deal, but if they won’t, switching might be your best option. 

Fortunately it’s pretty easy to do – our guide on how to switch mobile provider explains how. 

Get to know your new provider 

Before you switch, it’s worth looking into your new provider to make sure they tick the boxes. 

We regularly survey customers of 13 major mobile networks to find out their views on everything from customer service and ease of contacting the provider. 

Read our detailed mobile provider reviews for more information on your provider.