Just a further update on this one.
Have received the replacement gaskets & bowl, & these have now been fitted.
After full re-assemble, loaded with fuel, verified no leaks (yay).
However, still no joy in getting started. (Seems I may have actually inherited an S.E.P. as previously thought)
Bigted, would you have the valve clearances for this engine, may need to check those before proceeding ??