http://www.1sttopgear.co.uk/index.html are apparently good, have a few friends who have passed with them and a few using them now, only have good things to say about them. Also see quite a few driving around, and they seem alot less scary than some of the others. Good luck!
I learned with a PO WEM (O) in Gosport, who used to do lessons for a very reasonable rate (under a tenner). His name escapes me but I'm sure if you ask around someone might know him, there can't be that many PO WEMs doing driving lessons in a red Hyundai.