Brake problem

[leeroy]

Hi there!!
I'm having a problem with my front brake calipers on my vectra 2002 2.2 sri dti.
The pad wear worning light had come on for the front pads, took the car to my local garage but when they came to fitting and road testing the brakes seemed to stay tight on the discs,
took them back off and the piston on caliper didn't seem to move freely in and out like the top is wider then the bottom??
also seemed a bit weird having plastic pistons???
Can any body please help me out with advice on this as i am losing all faith with the garage!!!
thanks leeroy

[rushy]

Plastic Piston! Would that not melt! Have you taken the top of the reservoir to let the fluid flow back in as you push the piston back in? PS put a rubber glove over the reservoir neck.