From full bars to no service: Which? reveals the truth about the UK’s best and worst areas for mobile signal quality
Postcodes in Wales and the South West have been named the worst spots for mobile connection quality in the UK while areas in London and Nottingham enjoy the best signal, updated mobile checker tool from Which? reveals.
All of the Big Four mobile networks - EE, O2, Three and Vodafone - claim their 4G networks cover around 99 per cent of the UK but new data from Which? and Opensignal reveals the truth about how good the quality of that connection really is in your local area.
Which?’s mobile network quality map - powered by Opensignal - uses real-world data from consumer mobile handsets to create a percentage score for how consistent the signal is in each postcode area in the year to August 2025.Postcodes in Wales and the South West were rated as having the patchiest and most unreliable mobile experiences in the UK.
SA70 in Tenby - a popular seaside tourist destination which sees thousands visit during the summer - was named the worst postcode for mobile network quality. Mobile users only experienced a good connection 54.3 per cent of the time. This dropped to just 38 per cent of the time for Three customers. At the other end of the scale, EE and O2 customers enjoyed the best mobile quality in Tenby - with scores of 71 per cent and 63 per cent respectively - meaning these customers of these networks had a good experience around two thirds of the time.
LD1 in Llandrindod Wells was ranked the second-worst postcode for mobile network quality, with a score of 54.8 per cent overall. Three was the worst network in Llandrindod Wells with their customers experiencing a good connection just 41 per cent of the time. O2 customers enjoyed the best experience, with a score of 66 per cent.
In England, TA5 in Taunton and TR4 in Truro had the worst postcodes for network quality - with scores of 56 and 57.8 per cent respectively. O2 was the patchiest network in both areas while EE provided the best connection. Two other postcodes in Truro - TR27 and TR 18 - were also in the bottom 10 postcodes.
The research found that those in bigger cities - including London, Nottingham and Glasgow - enjoyed the best mobile coverage.
SE11 in London - covering parts of Kennington and Vauxhall and located just across the Thames from Parliament - and NG3 in Nottingham tied for the postcode with the best quality mobile coverage with a score of 87.8 per cent. All the Big Four mobile networks delivered consistent connections in both areas, with scores of 85 per cent or more.
Two other London postcodes- SW3 and SE27 - also appeared in the top 10 best postcodes for mobile quality. Postcodes in Sutton, Romford, Ilford and Glasgow also rated highly.
These findings show that the quality of mobile coverage varies dramatically across the country and choosing the right network for your area can make the difference between a seamless connection or a constantly patchy signal.
Virtual network providers, like Smarty, Giffgaff and VOXI, each piggyback off one of the Big Four networks, and users of these networks should generally expect similar quality to the parent network. Mobile customers can use Which?’s free mobile network quality map to check the coverage in their postcode and see which networks offer the best quality signal.
Previous Which? research found that smaller providers outperformed their bigger rivals in several areas - especially for value for money. Rolling monthly Sim-only contracts for the Big Four networks start from £19 whereas these are available for less than £5 from some of the top-performing smaller firms, with more data included.
Any customers who are nearing the end of their contract and are unhappy with their coverage should not hesitate to vote with their feet and move to a provider with better signal and value for money.
Natalie Hitchins, Which? Head of Home Products and Services, said:
“This research shows just how dramatically the quality of mobile coverage can vary across the UK.
“Choosing the right provider can mean the difference between seamless coverage or constantly battling to make a call from the comfort of your own home.
“If you are unhappy with your mobile service, use Which?’s free mobile quality map to find the best connection in your area. Vote with your feet by moving to a provider with better signal once your contract ends, and you could also stand to make a significant saving.”
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Notes to editor
Research
The Which? mobile quality map is powered by over 17 million network tests taken across the UK over the last 12 months from users of Opensignal apps and is powered by the same data as the Ofcom Map Your Mobile tool.
Based on ‘how often will it work’ scores, the map uses a percentage to represent how useful and consistent the signal is in each postcode area in the UK. In contrast, a coverage map would tell you whether or not a network provides coverage in the area, but not how good it is.
A higher score indicates that users enjoy a seamless experience for mobile apps like video, web browsing and social media, more often.
Table of results revealing the best and worst postcodes for mobile quality
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