26m people in the Priority Groups i.e. up to the 50 year olds.
We've vaccinated 10.5m as of 3rd Feb close.
7 day average according to the BBC is 431k per day. There are 26m people in the high risk groups so we have 15.5 m to go.
If we vaccinate at 431k per day then that's 36 days from the 3rd Feb.
Source for current rate:
bbc
Source for numbers in the priority groups:
health.org.uk
You can obviously tinker with the vaccination rate to see when you think the over 50s will be done. I wont give you the date because I'll get accused of being over-optimistic.
That moment is significant because 3 weeks from that date is the logical latest date for the lockdown to end. In the medium term we have to be wary of mutation, and variant evolving but I think unless that happens really quickly we can handle that with another round of vaccinations in the Autumn.