It's the 1st of month and saying 40s will start being invited this month means by 31st.
This is over 4 weeks away and given the massive upswing in vaccines about to be offered, it wouldn't be surprising if many areas have finished groups 5-9 in the next 5 weeks.
Currently over 60s can book on national site (group 7) and group 6 are being called by GPs. It takes a while as there are far more in Group 6. There are 2 concurrent systems..age based via national system, along side Group 6 via GP local hubs.
Even within this week, we are likely to move onto group 8.
It isn't inconceivable at all that they can whizz through 50s and be onto 40s, when over 2.5 million have been done each week and the expectation is for a big upswing.
If you know someone 60+ who hasn't booked (not group 6) then tell them, they don't need to wait for a letter and to get int he website and book and take an appointment sooner rather than later. If people get in the site as soon as their age group is eligible and take the appointments offered there, it allows GPs to speed faster through Group 6 and later age groups to get done sooner.
The things slowing it now are people not going on and booking and people deciding they don't want the locations offered by the national site. These age groups really just need to get on with it now and there should be less delay as we move down through age groups as less complications about things like travel.