Carphone Warehouse has said it could sell up to 10,000 iPhones on Friday and O2 is also gearing itself up to deal with huge public demand for the £269 handset.
The company is believed to have taken on 1,400 staff at its customer service centres and high-street stores, and ordered hundreds of thousands of handsets.
After the £269 upfront cost, customers will sign an 18-month contract with O2 on a tariff of either £35, £45 or £55 per month.
The £35 tariff includes up to 200 minutes and 200 text messages a month. This rises to 600 minutes and 500 texts for the £45 tariff and 1,200 minutes and 500 texts for the £55 tariff.
Apple has said it wants to sell 10 million iPhones globally during 2008.