Right postitive update here fellas.
New tank on and it runs like a dream. When I got the old one off I could see inside that the return pipe had such a build up of shit in it that it pushed the pipe off the swirl pot. I will cut the tank open later and get pics.
My fuel pump was fucked to start with, then my metering head had a plunger which was stuck and finally the tank was blocked. It is now sorted.
If anyone else has the same problem then give it a try.
If it won't run always check the fuel pressure!!!!!!!