Thanks guys.
Thought I'd share my experience whilst ordering new seats today. After deciding that the Roadster 7 seats wouldn't pass IVA, I decided to order some Recliner Sports Seats direct from Cobra. Having left 3 messages in 3 days asking them to ring me back which they didn't, I eventually rang Europa, spoke to a guy who evidently knew exactly what he was talking about, answered my questions precisely, couldn't have been more helpful, and charged me 60 quid less than Cobra were about to!! Job done!
Am working on a fairly simple solution to the bumper problem, basically involves sticking an extended ally piece onto the existing bumper and bending it round (i) back towards the vehicle (ii) within 30mm of the chassis/bodywork. Will post some pics when the prototypes are up to scratch