Trevelyan,
Kissmysquirrel probably realises that the post was asking for an IR school as not only is there a good groundschool company based in Bristol but there is also a good Commercial Flight Training Organisation called Bristol Flying Centre at Bristol Airport.
They provide CPL and IR modular training and have a very good reputation.
http://www.bfctraining.co.uk/
Best wishes,
Charlie Zulu.