Thanks you all very much for the replies.
I put new orings on the transfer tubes males and female, and had a fiddle with the transfer tube piston, but could not make it move. I put it all back together and now it seems to be working! Sometimes when I air it up it does seem to leak for about half a second until it seals and it's fine. Hopefully it will be ok!
Appreciate all the replies!
Thanks again!
Nathan.