Finally a few pics of the red disk peeping through the spokes.
And a few tips; A dremel with a rotary wire brush cleans the brake parts quite nicely, I wish I would have realised/remembered that a bit earlier. To jack the car up, I used a normal garage jack, and an axle stand. I put a piece of wood just in front of the rear wheel, and lifted as far forward as I could, and then I put the axle stand as close to the jack as possible. For additional stability I didn't remove the jack, but kept it slightly "pressurised"
Also, I was annoyed at not figuring out the rewind thing before I was doing the second side, so for the first side I sanded down the pads a bit, which now are a bit wonky and aren't gripping the whole disk. And they're also dragging a bit (which will wear off obviously). Hopefully it won't wear down the disk in a bad manner. Ah well, you live and learn.
Huge thanks to Martin for all the answers!
Tomorrow the car goes in to look at why she's playing up, and hopefully the electrical problem too.