An actually mechanically compentent friend over today to see about replacing the rear handbrake shoes to try and banish The Noise(TM). The suspicion was that the friction material had parted company with the metal of the shoe and was rubbing the inside of the top hat bit of the disc.

I'd been sorting some rust by taking it back to clean metal with a wire cup, vactan, zinc primer and then colour anyway, so put the Mercedes on the lift and took the wheel off, unbolted the rear passenger side caliper, undid the retaining bolt and took the disc off in prep. This uncovered an unexpected scene

Each shoe should have one retaining spring, except mine had two jammed in the lower shoe, and none in the top shoe, allowing it to flop about.

Further dismantling by showed the top retaining spring had pulled out of the backing plate and fallen to the bottom, where it had become jammed in the bottom shoe. The pin was scraping the inside of the disc top hat, and the floppy top shoe was not retracting properly. No flipping wonder it was making a noise! 

We disassembled and then reassembled it with the new shoes I'd bought, it's a fiddly old job on the w203 but all sorted on both sides in about 90 minutes. The driver's side was fine, incidentally, but replaced the shoes and springs for new since it was all apart.

We mounted the retaining spring the other way around into the backplate so it should stay put now. Replacing the backplates looks like a right old carry-on, involving removing the hub nut and probably necessitating a new wheel bearing so stuff that.

I have almost finished the repainting now, but it started raining so can't go for a road test yet. The paintwork should dry overnight and it's supposed to be dry tomorrow so will spray on some lacquer first thing, let it dry then go for a drive in the afternoon to see if it's sorted. Fingers crossed!