The build

I assume your fridge/freezer will be on the same ring mains as your battery, if full, should be able to keep modern fridge going for at least a week probably 2. We have a 1 kilowatt caravan kettle we can use to draw less power from a battery.

You assume incorrectly.  The fridges and freezers will just have to take care of them selves.  Generally if not opened during power cuts they don't defrost or warm up too much.  As long as power cuts don't last days.  Luckily those sorts of power cuts are few and far between.  If we do have a long one we still have generators

We have had some solar panels for a while and added some battery backup a couple of years ago specifically for the freezers in a prolonged power cut. So in winter they are kept fully charged. The whole house is switched on (manual switch) if there is a power cut and we would just have to not use any major power users - the kettle, oven/hobs ... and turn off anything not needed - dehumidifier, anything on standby (shouldn't be anything but probably the microwave) .

For Scotland, it is a pity you didn't gain independence before North Sea oil was developed - and the government used it for the benefit of the Country not the corporations. With wind as well now you cold be like Norway. You might need to rebuild Hadrian's wall to keep the hordes out.