As a conclusion (hopefully) to this tread I've gone back to an AAA carb needle, I tried it when I first fitted the Cooper head, HS4 and and 1 1/2" exhaust but it ran too rich so I went to an AAU which suited the cast manifold set up. Since fitting the new manifolds the car has been a bit kangaroo'y when pulling away gently and hesitant at low revs, winding the jet down made it better but resulted in a fast tick over even with the stop wound right back. So the AAA went back in and it's much better, smoother, quieter and adjustment available on the tickover screw again - plugs are a nice biscuit colour after a good run too so I feel it's pretty much spot on now
The nice black paint has burnt off the manifold though

Now where's that barbeque spray.