There was no rush to be fixed so it was as and when time permitted, i know it seems like a long time but total hours spent on it were not that much.
Ok, some of you will probably know this from another forum, but finally got the old girl going wed night, so firstly I would like to say thankyou to everyone who posted an idea or suggestion to help me resolve this dilemma.
The problem was failed O-rings on the stop valve, which is situated (for those that don't know) on the end of the H/P pump, taking this off was a little fiddly, but once done and having a look at it you could see the small green o-ring the white support ring were shot to pieces, the third larger o-ring was non existent, replaced the o-rings but unable to sort out the nylon support ring out, no bother though, that'll be sorts this weekend. Anyway once put back together without priming the pumps or pre heating twice it started first time first turn of the key.
Thanks again everyone