Superphil
Dismember
3 is utterly dreadful !! It's ok in a major city but go out of the city and no coverage.
EE is probably the outright best as you get TMobile and Orange networks to use.
3 is the only network that gets any sort of 3G coverage in the village I live in. All, that's All, the others struggle to get even one bar, O2 and Vodafone don't work at all. I guess it's down to where you live, rather than 3 being dreadful.
The best bet, when you decide where you are going to live, is to ask the locals what works best in that area/location.