Thanks all. We have him booked to see a paediatrician. I'd be very anti-drugs and although he can be hard work for teachers, he's bright and engaging too (they always seem charmed by him even though he frustrates them). He's much easier one on one, when he's not vying for attention I guess. We do use star charts etc and lists more so. Our current focus is on steering him through the 11+ (ie getting him to give of his best in the test itself) as I'd be happier with him at a school that will push him than one where he may end up coasting (as he's capable without much effort so I'd be worried that would be sufficient for some schools). Having said that I'm DIYing and whilst he doesn't always give his very best, mostly he seeks out his work, gets on with it relatively unbidden and does well.
Thanks again all.