Thanks for that John, I did buy a new piston seal but didn't realise there was a magic way of fitting them (according to Impact) and the mounting lug is now damaged and it won't sit straight on the piston, I'm a bit reluctant to spend another £30 on another seal, if I can get the power up first with a spring then I may consider getting an OZ piston seal and converting that to fit as the Theoben seals seem a little hard and un parachute like, someone said the Theoben seals aren't the best at sealing (might have been you), I may just get a no2 then and try that first.
Thanks for the advice John
Pete