Thanks guys....
Rich, I did check all the VAC's and I know where you mean but alas, they are all fine, if I pull a VAC out from anywhere the idle drops considerably which suggests that it's fine when all connected.
I think the problem is here
The warm up reg changes fuel pressure as the engine heats up. I suspect it's not working and therefore over fuelling once warm. Fook knows where to start but will check the basics at the weekend, power etc.... any other suggestions welcome.