It definitely wasn't showing OP on the gauge at the time, maybe the oil pump bypass valve stuck open but it seems fine now. I think I have worked out my pressure problem, I didn't have a valve cover breather that fitted so I stuck in a spare PCV valve but didnt have it connected to anything so am hoping that maybe that was stopping the engine breathing properly. I will run it with nothing in the hole and see if that stops the pressure build up.
Thanks