It's a pity that some of the responses to Bkin's post on this subject became so unhelpful that replies had to be turned off, because this is an important issue about health, and nothing to do with "snitching" or dictatorships. Perhaps any responses to my post could be more agreeable (I'm a sensitive person!).
Firstly, there needs to be an understanding about what is "advice" and what is the "law". The law is at legislation.gov.uk/uksi/202... (for England, though the legislation for other parts of the UK is similar). There is nothing in law about 2m social distancing, because this would be impossible to enforce (and I say this as someone with 36 years experience in law enforcement). So the Government have taken a different approach to this and banned gatherings of more than 2, which can be enforced, at least to some extent given that "gatherings" are not defined. However, I think most people can see the logic of this in terms of the infection risk.
Which brings me to the issue of what is reportable and what the authorities can actually enforce. You can. of course, report anything which infringes the guidelines, but the authorities cannot enforce it unless it also breaks the law (and please don't use this as an opportunity to reopen the debate on a certain Government aide!). Consequently, if you are of a mind to, you could restrict reporting to issues which are covered in law, such as gatherings (for instance, Manchester police have reported having to break up hundreds of house and street parties every weekend - these are clear breaches of the law and considerable contagion risks). I would tend to ignore fleeting gatherings because they won't be there when the authorities arrive (unless they are identifiable by other means) and present little contagion risk. Of course, it is up to the various authorities to decide their own priorities, and I wouldn't want to censor reports but, realistically, I would expect the police to concentrate on large gatherings (and there seem to be plenty of them!) which seem to me to be the worst offenders.