Thanks for all your replies, I'll have to check out the places you all mentioned, particularly Margate and Southend as those aren't too far away.
I agree with the poster that mentioned Funland in Blackpool, I won some good prizes in there.
The only one that was open when I went there at the weekend was Coral Island but that's quite good as sometimes you win tokens faster than you can spend them! They also let you exchange tokens for food and drink vouchers which is good!