Thanks, but trust me, there's far less ability than just blind hope and "let's give it a go" attitude at play here...

Made some good progress today.. the CDT trigger blade arrived from Dr Bob, so I now have a two stage trigger with a predicatable let off. Kinda felt like cheating when I'd made everything else myself, but it works very well.
I also made up the rear conical support for the barrel (and gave it a quick blast of matt black spray paint), and whilst it was out, I reamed the throat a bit deeper, to get rid of some notchiness loading some larger / harder pellet types.. it certainly seems to have helped.