//NJ, if you mean The Health Protection (Coronavirus, Restrictions) 2020, there are separate Statutory Instruments for each country.//
Yes I do, and thanks, Corby, you are quite correct (had I read the heading at the top of the document I would have known) :-(
I think initially they were identical but there has already been one amendment to the English one. Section six about leaving home has been amended to:
"...no person may leave or be outside of the place where they are living without reasonable excuse."
This was to overcome the problem where people were leaving home "with a reasonable excuse" but then remaining outside without one. If the others have not been amended similarly you can have the situation where someone living near the border can go outside their house in England (with a reasonable excuse), cross the border and remain there (without an excuse) perfectly legitimately and then commit an offence as soon as they cross the border to go back home.
It's a trivial example but demonstrates the problems that arise when a single nation has different legislation.
"...something called devolution
which you must have voted for but didnt notice"
I didn't vote for it and, yes, I would have noticed.