G'day all, thanks for all the suggestions, overwhelmed with the advice, thank you!
The pump is definitely the correct part and does work, i did test it i.e. was able to prime the system with the manual primer. I will check Boydie's suggestion on making sure the camshaft is in the right position when fitting and I will double check the spacer situation again. If no joy there, looks like it might well be have a look inside time for potential engine carnage!
Will keep you posted and thanks again to all.
Dave