I'm from Costessey Norwich, i use Combat paintball a lot and i can recommend any of there sites. They are cheaper because they have a bigger following.
Northwold has a supair field which i visited for the first time on a walk on Sunday, and had a great time. £20 and bring your own paint, what more can you ask for..
Warzone looks great, i visited there recently but did'nt play.
Have to say Top dog is very close to me, but have not visited there because you are not allow to use your own gear. They do walk on's but they will cancel if they do not get more than 10 people. I think after a bit of time they will get busyer, and that will change.
Necton site use CO2, and do not allow you to use your own gun. It has been at least 6 years since i last visited so un-sure if that has changed! I'm sure if i'm wrong someone will correct me.
I will be going to the next Northwold walk on with a few friends, if you come along, i will introduce you to a few people who i meet up with when i go to Combat paintball.