KN95 or N95 masks

Covid restrictions have been gone for a long time so things like mask wearing are back to the very low levels they were beforehand. So such things aren't as common.

A larger Superdrug or Boots is the best bet. You are relying on a bit of luck for a small pharmacy to have any - mine certainly doesn't.

You’ll certainly find the three-ply paper IIR type masks in branches of Boots. Some small supermarkets will also sell them (my Tesco Local does). For N95 masks you might need a bigger Boots - you can also order them online from Boots to pick up at stores.

There’s not a lot of mask-wearing in the UK these days.

The European equivalent to N95 would be an FFP2. You could check on the Boots website:
https://www.boots.com/boots-protective-ffp2-nr-face-masks-5s-10292473

This is a reminder to stick to answering the question directly, please. Per the addendum to our guidelines which remain in effect, avoid side commentary on anything relating to the pandemic.

Easiest way would be order some on Amazon to be delivered to your accommodation. I don’t think you’ll find them readily available as mask wearing is not common here.

My Lloyds pharmacy has them. Don't give up on a larger Boots or Superdrug until you have looked.

I've been traveling around the UK for the last 2 weeks and have seen few people wearing masks so I suspect the stores might not be stocking them much any more due to low demand

You may want to try the UK equivalent of Home Depot . Painters insulation installersother construction workers use them.

If you look on the Boots website link given in Laura's post you can check availability by store. So even if not doing click and collect, you can see where they are available. The brief answer is in lots and lots of Boots stores, especially in London.
They may not be on display, so you may have to ask a store assistant, but are very widely available at Boots.
You don't need other thoughts of internet searching.

Unfortunately, like most store stock information, Boots is not that reliable. Too often I've checked the stock at a local Boots only to go and find out they don't have the item.

But, Boots, Superdrug, Lloyds Pharmacy (found also in some Sainsbury's) are your best bet.

If not, and you have an Amazon account at home, you can log into your account on Amazon.co.uk and order them. I had an order delivered to me in Scotland earlier this week. (Hint..you will be asked if you want to pay in dollars or pounds. Choose pounds. While the conversion rate is good, they charge a conversion fee.)

Unfortunately, Amazon Prime is not transferable.

Thank you for all your help. I have checked out several Boots. The closest they have are cloth masks. I did pop into a travelers clinic in Victoria Station and they gave me a fist full of surgical masks free of charge. They aren't the best, but they are better than cloth. I will use them until I can find what I need. Thank you.

Seek and he shall find. Finally found KN95s or the European equivalent. Had to go to Canterbury Boots (I was visiting the cathedral with a different tour company). They had five boxes with five masks in each. I took three boxes so I'm set. Thank you to all!