Well, spent another afternoon trying to sort this bl***y rifle. In the end I managed to cock it, but really had to slam the barrel back into the cocking position. Obviously no good like this. All the parts look in perfect condition, trigger, piston etc. Such a shame as it`s a lovely rifle sitting in a walnut stock and very accurate when it works.
I`ve just assembled it and put it in the gun cabinet as I am really peeved off with it at the moment.