thanks for the reply that was really helpful.
I took apart the top section of the suspension, upon inspection the o rings, circlip etc looked fine but what i found was that where you insert the allen key to adjust the preload there is a very small screw at the bottom which was slightly loose (on both sides of the forks), I tightened them up and its no longer "hissing" on compression or at stand-still. I was wondering what purpose these would serve at all (pressure release?)?

Forks still soft but thats just the stock spring i guess, probably best i replace them at some point...

thanks again for your help! legend.