Well, problem solved, I mixed up some Dolphin Glaze filler last night and flated it this morning.
I then mixed up some epoxy primer and realised that what I had been using was primer without the hardener that I had mixed up ages ago, so sprayed on the new primer with hardener and bingo all fine, have given it three coats of primer filler put the valence by the log burner in the workshop which will give a gentle heat overnight.
In my defence I had a head injury that required surgery, a bleed and clot on the brain so when I mixed up the original primer had not put the hardener in with the primer.
Thanks for the replies all good information to take on board.
Steve