I had a very sticky rear caliper on a 156, but managed to get it moving by
dripping break fluid around the piston/seal, applying pressure using a
G-clamp, and simultaniously twisting gently with some mole-grips!!
A bit extreme and time consuming, but got there eventually.
I was only doing this to push the pistons back in far enough to fit new
pads!!
> Well, I got the piston out by unscrewing it from its shaft in the
> cylinder. However I'm b***ered if I can get the thing back in again
> with its seal. It's going to be a long night...