Now that all of England is in lockdown only essential shops will be open, which means that bookshops will sadly have to close for the duration. That's scheduled to last a month, but frankly if we have any chance of cutting the spread of infection down then lockdown really needs to last a lot longer than that.
I'm sure you all have more important things to concern yourselves with right now than comics but if you were thinking of buying any annuals for Christmas presents then your best bet currently is to order them online. Yes, supermarkets will be open and normally have them, but it doesn't look like my local Sainsburys is stocking them this year, so I don't know if that's the same across the country. (My branch has also cut down its comics stock to a few pre-school titles only. It hasn't had the Beano weekly all summer.)
If you want the annuals by Christmas then ordering them from the D.C. Thomson shop is a good bet. You can get The Dandy Annual and The Beano Annual individually, as a double pack, or as a triple pack with the Beano Christmas Special. You'll find all the DC Thomson books at this link:
(While you're at it, I'd recommend a Beano subscription too, considering that shops will be shut.)
To illustrate this blog post I've used a couple of bits I did for The Dandy Annual 2021. You'll see the full works in the book itself!
These are very difficult and unstable times for all of us so I wish you all good health and peace of mind.