Slightly before my misfortune with bending the forks with these brakes I gave them a service as the braking power had dropped off a little and they had a tendency to stick which was becoming really annoying. I had this problem happen once in the past and it was alleviated by deglazing the linings and chamfering the edges. I'd done about 8000km over two years through rain, snow mud and grit so I decided to give them a quick look and a little maintenance, they've been otherwise pretty maintenance free which was one of the main reasons I chose them in the first place.
Disassembly is pretty straightforward, the locknut on the hub is removed on the brake side, and the cover plate and drum mechanism comes off. One of the star lock nuts has to be removed to allow you to release the shoes themselves, they can be levered off with a screwdriver. Try not to re-use the old one, particularly with brake parts it's better to be safe than sorry. A new replacement star lock washer is available for 50p. I thought I might give the pivots a look at, maybe they were a bit dry and could have contributed to the sticking.
Even after 8000km or so there is still plenty of pad material left on the shoes, I gave them a quick deglazing and a chamfer again. Be careful not to get any grease on the pad material or it will be contaminated and affect the braking.
I checked the pivots and added some copper grease to them. It's better to use copper grease over conventional grease as it is made for high temperatures as well as a tendency to stay put and migrate over the braking surfaces.
The star nut was replaced with a new one which is 5/16" or 8mm size. Use a socket (a 9mm or 10mm socket is close) and give it a tap, enough to secure it in place but allows the shoes to move freely.
Once that's done, I put it back together again and the braking power was back, and there was no sticking whatsover. I've been riding it now for a few months since then and it hasn't come back. Hopefully this should stay like this for a while.'
Update March 2014
The sticking has returned and I've again serviced it in Part II