Hi AVB and Tyler,
I'll take all this fabulous info on board and give it another strip down on all sections of the fuel system and while I'm at it I shall add a new diaphragm, this way all will be completely replaced.
I push lots of throttle body cleaner through all orifices and it certainly had a few blockages which were cleared at the time, but who knows until you try again.
Thanks again and I'll report back with the findings and results.
Cheers,
BB.