In reply to MargieB:
It does look a bit as if, currently, at Tier 2 it's easy for R to remain above 1 (worsening), and Tier 3 seems to bring R to about 1 in most areas (it's stabilising at the current levels, not improving but maybe manageable).
But it won't be as simple as that, different areas have their own quirks and the coming winter months may naturally raise the spreading rate anyway, such that Tier 3 isn't enough to keep it stable any more. (And conversely, when spring comes on, Tier 2 might be enough to keep it stable in a lot of places.)
Fingers crossed, we hopefully just need to keep it stable until we start seeing the benefits of part of the population being vaccinated, now. That just might get a bit harder during the cold, dark months.