It's a toss up really isn't it between the rights of those whose health conditions mean they can't wear a mask, and those, formerly shielding people, whose health conditions mean it's not safe for them to shop if there are too many (possibly any) people without masks.
Both can't comfortably be in a shop at the same time. So either you have mandatory mask slots, or specific slots for those that are exempt -forcing people do to their shopping at a particular time, or one of the group's needs to stay away from the shops.
Given the shielded have been required to hide away for months, I'd rather they shop safely at the moment, and masks be truly mandatory.
And yes, that means no unmasked children in shops either (young ones could be in buggies with rain covers over it?).
If we had a similar proportion of people claiming exemption as other European countries, then that wouldn't be so bad, but it's illogical that we have such a higher proportion.
I find it quite disturbing though when the response to 'they wouldn't like an oxygen mask for Covid either' (which you would be conscious for) is met with 'it would be really difficult, but I'd manage' - Whilst I understand that in life threatening situations, people can do extraordinary things to survive, when it's not quite so extreme, it feels like some are willing to do it for their own welfare, but not to protect others.
If compulsory use of masks is to continue, I think we need a system of exemption cards, so that those whom a Dr sign off as being exempt (can be done via a phone call consultation) get an official card, which gives no details as to the reason for the exemption, but is proof of it. Then those without the card either don't get entry or get fined.