I just wander.... UK has 67m people.
700k are on the autism spectrum, and let's assume 350k are severe.
about 100k have Trigeminal Neuralgia (me being one of them)
So that's about 450k people who genuinely have a reason to not be able to wear masks.
PTSD due to rape/abuse surely doesn't fall into the 100k+, so let's say 50k have severe PTSD (god, I hope I'm overestimating!)
Around 1m have severe asthma.
This gives us 1.5m people. That is less than 2.5% of the population.
Now: think back to being on the streets and out'n'about. In your head count the number of ppl you say total and how many didn't have masks. I am pretty sure that if you have a big enough sample (eg: sit on the steps on Trafargar square, or in a big sainsbury anywhere in london) you will see a much larger porportion of ppl NOT wearing mask than 2.5%. I appreciate that small communities may be better, I don't know. Locally in SW London the picture isn't any better for sure.
Even if we account for many other medically reasonable conditions my guess would be a max of 3%.
(I didn't count the 11m deaf or hard of hearing people, as in general setting they are not the ones who have a problem with having a mask on, their issue is others having one on, but there are alternatives to that. Education/workplace is very different)
That means that if you see 50 shoppers in tesco, then a max of 2 should not be wearing masks.
I went to a big sainsbury's a few days ago. Saw probably less than 50 people (I was in and out in under 20 mins. never liked shopping in general) and people with masks on: about 5, incl. me.
It really baffles me how the minorities have such a huge voice in the UK. Every minority is as important as everyone else, but not any more than the majority. And there will always have to be reasonable compromises made.