Just re stripped the TX and removed a slip washer that I had put under the top hat......It now cocks.

With a Mk 3 V-Mach spring it makes 8.5 f lbs, with the Mk2 Knibbs spring, its at 11.2 f lbs.

New seal, so will put a tin thru it and recheck.

Many Thanks for all of your comments...shame I made a school boy error

Cheers

Steve