Thanks for all the comments. Currently waiting on the CAA to get back to me. I have had to send them a detailed email which apparently goes to some 'policy group', even though its all in black and white in lasors.
Big Grecian, my flight school is very good. As they hadn't done this before, i.e someone with an FAA IR, they wanted the CAA to clarify. I'd rather them do this then send me down a blind alley.