Finally got round to checking on the rear brake caliper. I mentioned here a few months ago that the pedal was hard and the offside rear disc wasn't being cleared while the others were.
Took everything apart and cleaned it all up using brake cleaner. I thought that it might be the pins that had seized and the pads weren't returning, but they were smooth and clean. Wound back the caliper for good measure. Took the disc off as well and noticed that there was a mark on both sides from where the handbrake had obviously been left on for a good while, so cleaned that off as best as I could. Put it all back together again and turned the engine over and pumped the brakes, and everything felt smooth, with maybe a little more travel on the pedal than before, but none of the hardness I was getting.
Haven't done a road test yet, but will probably pop out in a little while and go round the block.
Hard to believe I replaced this caliper in January. The state of it...