Well, it's been a quiet couple of weeks on the build side of things as I've been waiting waiting waiting for some bits to arrive. What I have managed to do it get the blasted stuck piston out of the rear caliper. I tried the air compressor and reconnecting it to the master cylinder to force it out under hydraulic pressure with no luck. I eventually resorted to brute force - soaked it for a day or so in brake cleaner then worked it loose with a pair of multigrips. Mangled the top of it but got the bugger out. I'd say it had been stuck for some time as the brake pads had been worn on a pretty steep angle. So I've got new pistons and seals and have a new set of pads on the way.
I found a rear hugger for my model on the French Ebay of all places so that is wending its way over the turbulent Euro seas before the entirely of Europe goes up in financial flames, along with a top triple clamp adaptor so I can put a set of drag bars on instead of the clip ons.
I'll stop spending money on this bike one of these days!