On the health anxiety in terms of asthma my advice would be to talk to people about it privately
. Health anxiety is something which is being talked about an awful lot at the moment in the volunteering I do. I know some people with very high levels of health anxiety normally and they say they aren't really affected by covid-19, I've met a lot of others with OCD and GAD who are pretty worried and showing health anxiety-like symptoms.
I know a lot of people with asthma. I've only heard of one that has the letter. This doesn't actually surprise me in the slightest (5.4 million people in the UK have the condition which completely dwarfs the 1.5 million letters - source PSNC), but I know saying that is likely I get punched by you and other people on here who are understandably worried. Emotions/tempers/worries flaring up massively for some of those people. One is still raging against the world, but especially the GP after having not got a letter and trying to register and it being declined by the GP. Despite writing some time later, they are still having a lot of problems with deliveries. Some other people I know have been reassured that they haven't got a letter.
Yes, I believe one person on here has a letter for asthma (as a precaution, as outlined by Dr Harries DCMO).
P.S. I can quote some stuff about asthma to put it in context even though you have asked before, however, for two posters I simply think that would be unhelpful and counterproductive, so I haven't done it.