as said already twice, just rewind the piston back with the rewind tool.
one question i do have though and sorry to hi-jack the thread.
i recently did my rear pads and tightened the handbrake cable as my handbrake was quite poor. do the cables stretch quite easily on these cars as i found as soon as the handbrake was working corrrectly i got quite enthusiastic with it

and now it works like it did before i adjusted the cables...
