Rear piston won't unwind

[Mada05]

Grr, following on from my thread earlier about my rear discs, my rear passenger side piston won't wind in anymore. Its stuck fully out, I have tried turning it with a screwdriver but this is not working. Any ideas?

Edit: The brake resovoir is undone.

 

[ben_p]

wd40...and lots of............... there is also for winding them.. most factor will sell it

 

[Mada05]

Right, got the piston in. Now I can't get the caliper (think thats what its called, what holds the pads) to line up with holes on the side of the brake asssembly.

i.e. I can't mate these holes upto to the sides of the brake, its about an 1/8 of an inch out :