okay, so i took the caliper off to take a closer look myself.
there are no "self adjusters" as such.
the centre of the piston is on a screw and the screw is the adjuster, as it is for normal pad wear.
that can be screwed in and out using the tips of a 20mm spanner.
the handbrake operates from what looks to be an internal cam that pushes directly onto the piston. this gives total handbrake movement of a few mm in order to engage the braking system.
there is what looks to be quite a heafty return spring for the handbrake mechanism which is connected at one end to the bracket which operates the cam and the other end to a bolt which operates as a stop point either way for the handbrake.
i took off the sping, took off the bolt then kept worrying the handbrake operation back and forth until i could move it with just hand pressure.
with the bolt out i was able to go just a little either side of the stop points in order that the full available area for normal usage was clean and working.
i opted for this rather than taking the piston out to avoid damaging any seals, which would have been the only other alternative, as there were no external fixings fot the handbrake mechanism. my guess is that it's held in place by circlips on the inside of the caliper.
so this was my cure in case anyone else experiences something similar, although i doubt it as most appear to have drums rather than discs.
no, i didn't take any pictures in case anyone was about to ask.
