Well I think I may have found the cause, although I have still got to get the bits and get it rebuilt before I can try it again!

Basically took the engine out last night to leak test it and straight away I noticed something that looked a miss! Not only is the exhaust gasket (rubber/silicone top hat style gasket) absolutely destroyed, but it appears that in a previous rebuild someone has failed to replace the head gasket!!

Cant believe I havent noticed before but it certainly doesnt appear that there is a head gasket fitted, I assume this is almost definately a cause for it not starting and would explain alot really!! I assume the gasket would just sit between bottom and top ends of the engine, it wouldnt be fixed as such would it?!

I have since found a place which sells the gaskets so ive ordered them up, also ordering a new glow plug and glow starter as I dont think either of mine are working properly plus its one more thing I can eliminate!