Common Sense suggests that nobody should mix with anyone else. Though reality is this is not always possible.
If the government had to legislate for every conceivable variation, well, that would be unmanageable. Trouble is, the British Public, as we know, are incredibly thick and, as has been stated, aim for the rules to be the target they must meet*. And the authorities are pissing in the wind by trying to rely on the common sense of the populous. Personally, I think all parts of the Great Britain (not sure on NI's current rules) have implemented the least restrictive rules possible given the circumstances, I think they do need tightening... ...this new more infectious strain is clearly now everywhere, so I think everywhere should be a minimum of T3, and most places T4.
I'm in T2, in a commuter town, a few miles north is the T3 area spreading south from the midlands, and 1 mile south is T4. Its a bit non sensical, as a significant proportion of people are mixing to what the rules allow.
Whilst I'm pretty confident if/when I catch it, I probably won't notice any more than the usual colds I get this time of year, it would be likely I would spread it to someone (directly or indirectly) who would not fare so well.
Hindsight is a wonderful thing, but I do think the government has always been slow to respond. For the current extra restrictions, this was obvious early last week when the numbers started to rise significantly. Other than that, I think the government has done a reasonable job... ...and the mainstream media has done an absolutely crap job, even by their pathetic standards.
*But these same people refuse to use the speed limits as a target, and drive at 15mph below them
