Phil,
Only the early cars (up to the 1980s?) had the square brake adjustor on the back plate. On these, brake adjustment was a piece of cake and you could always adjust up or down to suit.
I understand why the self adjusters were introduced, but it does make the job more difficult.
Apologies for asking the obvious but you haven't got the car in gear have you? If not then follow Jay's advice above, but be prepared to use some substantial tyres levers to prise the drum off , if all else fails to shift it, you might need to replace the shoes after doing so. I would also put a regular rear drum removal and inspection on your maintenance rota.
This brings me to another personal crusade, if we don't use our cars things will seize up through lack of use. Cylinders are much less likely to seize on well used cars.
