legislation.gov.uk/uksi/2020/129/…
thegazette.co.uk/notice/3495369
That was before Gov moved to 'stay at home if you're infected'. But powers can still be used.
The regs are made under Public Health (Control of Disease) Act 1984, which doesn't apply to Scotland or N Ireland, so no regs were made there. legislation.gov.uk/ukpga/1984/22/…
* Wales has its own, essentially identical Regs.
Again, none for Scotland of N Ireland
Current draft here (but expect at least minor changes) publications.parliament.uk/pa/bills/lbill…