I decided to have another look at my pressure this morning - as I have changed the oil, I thought I would see if I could work out how much went in. As I used a new can I poured out the remaining oil into my topup jug (Nice green quart Castrol one) - and it went way past the quart mark and was about to spill and there was still some more in the can
So I poured half what was left back into the can to leave me with about 0.5ltr and poured that into the engine (Bearing in mind the dipstick was showing full already.
So its now showing well full on the dipstick
But started it up - still getting the initial 50psi after a couple of seconds to then fall back before rising to 80-90 and staying there until it warms up - so I think unless it blows up before then I'll strip it down next winter and see what the issue is. (though I'm trying to sort a shorten drill bit to clean the PRV seat in the meantime too) But after a few miles with the engine hot (oil may not be fully hot to be fair) but it did look a better pressure.
Its also running alot better now I have the manifold leak sorted - does actually idle below 1000rpm. Need to twiddle some more as the needle is now, in theory too lean for the exhaust etc.