You have some sympathy from me sparklykid in that we share some frustration at the way some blatantly abuse it and sellfishly show disregard for fellow members of society. But at are store we stopped challanging non-mask wearers as it just led to confrontation or we were ignored/dismissed with 2 words or a glare/. We found the best method was to offer a free face mask at the door to anyone without one but even then quite a few (yes, often but not allways men in 20s-early 40s in site working clothes) just walked past us. Fortunately most of these younger ones had just nipped in for a bottle of fizzy drink and some crisps or chocolate bar so were in and out quickly.
Its not worth confronting them sadly. A did it once in another shop when someone was telling customers how covid was all a hoax but a got answered back by someone who called me a sheep and wanted to lecture me a youtube video and a wished had said nothing as a came out flustered and he looked pleased with hisself/
Its a very British thing that we make excuses for these people- oh they may be unable to wear one for health reasons- but we can know theres not that many who are that unwell. In some other countrys theyd be refused entry or the staff or public would make them feel uncomfortable, and police might enforce it. We'er too polite here- some shops have signs up saying please recognise people may have dissabilities so be understanding if they dont socialy distance or wear a mask dont challange them, Fair enough for some but it does give an easy get out for the sellfish too.
You were brave to post on here sparklykid, but a knew straight away you'd get some stick and theres a small chance it may have been due to there disability. On balance its best not to make a scene in Britain. The best you can do is make it obvious your keeping a distance - leave a 4 metre gap in the queue if you can and cover your face up even more- put on a second mask and apply some extra sanitiser (or if your feeling brave cough a few times)??