Thanks for the advice. I always back off the adjuster before I attempt to remove a brake drum. There is often a lip of unworn brake drum on the inner edge on which the shoes can catch. Then the drum sticks, hammers are used, then tyre levers, and finally the shoes break the retaining spring pins and the whole thing falls to bits. So now I always slacken off the adjusters first.
In answer to earlier questions, I had a pair of new drums kicking around that I had bought for a 2 litre job but decided the existing drums were OK. Then I overhauled the 3.2 handbrake, and as one disc had a tiny edge chip I decided to fit the spare pair. Like others I had assumed all Omegas rear discs were interchangeable. They fitted all right. Big mistake. Luckily I read the thread.