Wow, your learn something new everyday, a very interesting discussion of pad materials, and thank you DaveW for your link to Mulfab, I do believe the calipers are from a Sierra Cosworth as I surmised.
It was hARPpy chappie who posted about KH changing his pads, but having spoken to them it appears that what they actually did was change out a set of faulty calipers, which I assume had new pads too, but they didn't go on to say what the fault was on new calipers, possibly more to this than meets the eye?
It's not that the handbrake really bugs me, as it is just about OK, and I leave it in gear too of course, but I like a challenge, so if I could do better than MMC it would give me some satisfaction.
Apart from pads, what I will probably try next is to increase the leverage under the handbrake lever itself and see if that helps. I just need the time and inclination to get out into a cold garage and play around for a bit.
