I know that Southend Flying Club, Booker Aviation (Wycombe Airpark / high wycombe) and Stapleford offer the CB-IR courses.
I also know that White Waltham (WLAC), Alouette (Biggin), Surrey & Kent (Biggin), EFG (Biggin), Redhill Aviation Center (Redhill), amongst many others offer the IR(r) rating.
If that helps at all?