I have to agree with poisonivy.. I started off using o2 but their calls and rates are just as expensive and even though you do get free wifi spots with them in a lot of places in the uk 3 offers true unlimited data for £15 a month and on the iphone its easy to use 5GB+ a month.. or if you are looking for cheap then GiffGaff could be good, they use the o2 network but are able to offer cheaper calls and texts and also offer unlimited data (within reason) for £10 a month so I would go with one of two networks, though ever since people are abusing the GG network they might be stopping unlimited data and for that reason I use 3..
Vodafone,t-mobile,orange,tesco(they use the o2 network) am I missing any other carriers? They dont offer very good deals.