I ordered a "Stage 1 tuning Kit" from a guy on ebay. Comes with a whole bunch of replacement o-rings, screws, bolts and a "High performance" spring and a DVD.
It arrived on Monday so tonight I spent an hour reading through the instructions and undoing my "baby".
I replaced the hammer spring and all the O-rings, and a few bolts that looked old and gassed it up again. Oh no Air coming out the barrel! I figured out that when it's totally empty I might need to cock it first. Worked fine after I did that - everything still works, but I will definitely have to de-tune it using the power adjuster. (Have to buy a torx T10 first) It sounds as if a lot more air is coming out with each shot.
Just for the record, all the stuff looks like genuine Air Arms stuff. I honestly can't tell the difference even under a 10x loupe, so it's not cheap knock off stuff. The ebayer reckoned the fpe would be up to 25, but I think I'd need to test that!
All comes with a DVD with Instructions. If anyone wants the instruction pdf's I can upload them for you. (6.75mb)
I'll re-zero my scope on Friday! Maybe HGS has a Chrony and he can test it.