Made a start on changing the rear discs and pads today and almost everything that could go wrong, went wrong.
First thing I found was the drivers side caliper was siezed. When I did the fronts, my neigbour was able to refurbish the calipers with little difficulty, but this time the rear caliper proved too far gone and he ended up damaging the siezed piston when trying to extract it
I also found that the brake shoes were severley worn and the friction material was beginning to seperate on one shoe. I had hoped to get away with not replacing the shoes as they should be just for holding the car still rather than stopping it, but I do now recall the previous owner telling me he liked to pull the handbrake one periodically to clean the brakes, methinks he did it too much. A trip to ECP got me some new shoes for £16.
I also found the back plate to be severley corroded, one of the shoe pins for the retaining springs had actually rusted free from the back plate with a rusty hole where it should have sat. I was able to fabricate a bracket for the pin using a mending bracket and was able to locate it as an interference fit on the back of the plate.
The final problem came when trying to remove the siezed caliper, the union to the brake pipe had also sized and we ended up rounding it off trying to free it. In the end I decided to snap the pipe and source/make a new one.