306 rear disk brakes

[Babyben]

I have a 306 HDi and I am trying to change the rear brake pads. Simple as this should be, I have run into trouble.
It has single pot rear disk brakes, I have got the old pads out but cant get the piston to retract back into the caliper. I have tried all sorts of excessive brute force techniques, but it just wont budge.
I dont think it should be siezed as all seals etc are fine and it all looks in good condition. Does anyone know whether these brakes are screw in or need a special tool or process to retract them?

Any help would be good

Cheers
Ben

[bobseptic]

stupid question maybe, but have you took off the cap to the brake fluid?

[andyq]

To retract the piston you have to turn it, clockwise i think when looking on the piston face. Use the blade of a screwdriver or file edge to turn it.
It helps to simulataneously push on the piston face whilst turning with a second levering device. There is a groove across the piston face and this must be horizontal when you have finished retracting the piston.
The brake pad with a pip on it must fit against the piston(to stop it turning) with a plain pad opposite.