I take it a CBi would do as well although you may well just need to be checked out first as there are slight differences. Actually, if you are going to a school you've never been to before, they may well want to check you out anyway!
Try, in no particular order
Sterling (norwich)
Bournemouth Helicopters
Biggin Hill Helicopters
Oxford Aviation Training (though not sure about SFH)
a few good sources of this sort of information is the British Helicopter Advisory Board's handbook which lists all members and which aircraft they operate, G-INFO section the CAA's website where you can search for all UK registered S300s (Hughes 269) and their owners plus a search on google will turn up stuff!
I know there is somewhere in Devon that operates a Schweizer, and somewhere oop north plus I have a feeling that Great Dane Helicopters do/did was well and they're based Wales!
Cheers
Whirls