Yes, im sure that's the school.
Play.com and Amazon.co.uk are very useful too. If you're in an airport and you have time, check out World Duty Free, Dixons Electricals which is owned by the same group as PC World and Currys. Theyre sister companies so they have similar pricing on their products.
Im on a sim-only contract with T-mobile. For £10 a month i get 300 minutes, 300 texts and Unlimited Internet (1GB) per month. That is because I managed to get it cheaper because of being a customer of theirs for 2 years prior to extending it. The great thing with T-Mobile is that if you go over your data allowance, you will NEVER be charged more than the monthly fee that you already pay. not a penny more.
As T-mobile and Orange are about to merge together, you can share the reception signal from both networks.
I think their pricing and service are pretty competitive, so you should be able to get a good deal here. They also have some good international deals if you wish to add them to your phone line.
3, virgin mobile, tesco mobile (from tesco superstores), and talk talk (from Carphone Warehouse) are pretty cheap - but thats because theyre not as major as the companies listed below - and so you might want to check out their websites and see how the 2G/3G reception is around the cheltenham map area.
The major networks here are O2, T-Mobile, Orange, Vodafone and 3.