@Reastie, no massive isolation is a genuine problem, as it doesn't matter that each wave is distinct, if there's no-one working in London, then it doesn't matter much if there's a load of delivery drivers in Manchester and like Christmas as JoanOgden says, moving them would also rapidly move the virus.
However, the indication from other countries is that recent Delta infection is protective as are boosters, and if you don't isolate contacts (which you shouldn't as it's going to be increasingly likely that they have already had it, and it achieves little anyway at the prevalence and infectivity levels, other people are still there unknowingly infectious) then I think we'd be okay.
It depends if the Gauteng proportions of susceptible follow through here or not, if they do, then we're okay - although Australia / New Zealand etc. have a bigger problem.