Hello i have completely the same issue at the moment mate, taking mine in...thing is I've replaced all my rear brakes with brand new callipers, pads and disks and it has started to stick again. It seems to be very common with these cars. I originally thought it was the clutch. But i realised that when i was on a hill and the car was in neutral with the handbrake off it wasn't rolling back.....and thought to myself again???? grrrrrrr. I am not actually sure weather it is an issues which goes further than just the calliper because I've changed mine twice now??