All fixed now
I removed and stripped down the carb today and there was some sediment in the bottom of the float chamber, and oddly the whole thing seemed quite gooey inside almost like engine oil in it
anyway I washed it all out with petrol and blew out the main and idle jets with an airline. Cleaned and regapped the plug, swilled out the tank (which was clean anyway, nothing came out), flushed through all the fuel lines and then blew them through with an airline (not while attached to the carb I hasten to add), took off the fuel filter and flushed that through.
Reassembled and filled the tank up to the brim with fuel and it started on the 3rd pull which is a bit of a difference
after it had been running for a while it would start 1st pull just like it should and idle smoothly even in gear in the tank.
Must have been some crap in it from the factory I think, but normal service appears to have been restored
need to check it properly next time out and give it a decent run, but it works as it should running in the tank.
Still not sure about the lift pump though, I still think it should suck fuel up otherwise there isn't a lot of point having it...
For anybody else that needs one there is an exploded parts diagram here: