Well first of all the suppliers (not the makers) of the jacks told me 200psi should do it, then when it didn't I asked them and they said they got the calculations wrong and that I needed 280-300psi, but in fact I needed to get it up to around 350PSI. Ideally I think it needs a bit more, but the electronic valve block that I've got that opens and closes the air supply will only technically handle 300psi so I'm outside of the spec at 350psi and if I run it higher the solenoid can't open the valve so what I've got will have to do till I can get a higher spec valve block or I just decide to be happy with what I have.
I will send pics of what I've ended up with later today or tomorrow so you can see what the new setup looks like.