Just changed the rear pads. As I was winding the rear left piston back the rubber piston gaiter had stuck to the piston so was twisting on the piston as it turned. I wd40'd it and tried to free it up, I believe is just sits in a collar and rotates, it only acts as a dust shield I believe, in the end it didn't free up on the outside but rotated on the inside. It looks like a badly rolled up sleeve.
Now it's probably not a huge problem but I should probably strip and replace it? It's not holed or anuthing. The other thing is, the adjustment seems to be taking forever to come up. I've no leaks are anything and the pedal feels fine although for new pad and discs the handbrake hasn't gained any grip.