Well, now I've fitted brand new drums and shoes on each side, adjusted the "self adjusters", and still the brake comes on harder on the nearside. If I apply the handbrake going slowly on a stony track, the n/s wheel will lock up, the o/s won't, but it does still come on quite hard. The MOT man says they should be balanced, so it won't pass!
The adjusters are set so that the brake shoes just touch the drums - by now I should thing they've bedded in to just clear them. I've put a dob of grease on the brake cable where it goes through the eyes welded to the "axle". There's an adjuster at the middle of the axle, where the handbrake cable comes in from the lever, I don't know whether this is a balancer or just a brake lever travel ajustment.
If anyone can tell me how to fix/adjust this, I'll be very happy indeed, and "legal"!
The good news is that the new drums/shoes have cured the awful brake judder!