We too are hoping that this year's rules include that water birds do not have to be locked in, for their welfare. It went on until spring the year before last (was it?)
We shut our hens in the polytunnel for the whole of that winter - it's fairly large and they were happy as sandboys. Rats were a problem inevitably, and our winter brassicas were destroyed. The geese we walked to the veggie garden, which is fenced, each morning, and back to their house each night, minimal fuss, no wild bird incursions.
Just like Norfolk (I used to live there) here in Scotland we have no cases so far, but we do have a lot of migrating birds. We feed our wild birds in the front garden, to which our poultry has no access. I judge the water fowl risk by the number of splats on the polytunnel - only a couple in 25 years, as their usual route is along the river, down in the valley.
Last time, people made make-shift enclosures of any materials they had, the most important bit being to cover the top to keep out contaminants, or they adapted other sheds (maybe a garden shed and make a wire mesh pen for grazing). Usually there are enough bits of wood and so on which can be repurposed to make your enclosure. Four geese are not many to make provision for - think of all the free range Christmas turkeys which will suddenly have to be housed for a couple of weeks.
I'm sure further guidance will follow, meanwhile, unless you want to eat your geese for Christmas anyway, spend the time constructing a temporary enclosure for them. Ours are pets and they will survive!
Above all - DON'T PANIC