Cheers for the suggestions guys. Been a bit manic trying to get the bike sorted and also the van repaired after a head on crash a few weeks back.
All done and now on Naomi's masterclass tour of England.
I had a shop purchase and fit a new valve only to find out that when I picked it up off a mate who'd collected it for me, it has not worked and just lost pressure when I sat on the bike(bike went in with no wheels on..)
Ended up going with fatdoc's plan and popping into winstanleys and buying a new shock off them. The chap in there reckoned the old shock may have a broken seal as he said that would have been the popping noise a heard( had forgot about that until he asked me!).
On the plus side I've learnt how to fit rear shockers in a Sheffield premier inn room!!!