This really is for none mask wearer's (if any at all )
KNOW THE LAW!
Remember, according to social distancing, shop staff cannot “touch” you or come within 1 metre without breaking guidelines, (but of course they touch everything you’re buying) ?
and if you refuse to wear a mask in their shop they cannot physically throw you out, but can only call the police to enforce a government 'guideline'. The big problem for the police is that that would be breaking the Law if they tried to enforce a 'guideline', because police can only legally enforce Criminal Law.
If the police detain you, or arrest you because, naturally, you have refused to cooperate, they are then guilty of unlawful detention, which comes under the criminal code of 'kidnapping'.
If they try to fine you, without first 'kidnapping' you, you are not obliged to give them any information, not even your name, and without your name they cannot issue a fine.
If they find out your name, by whatever means and then issue a fine, you can simply state that you refuse to accept or pay any fine and they will then be obliged to caution you, which would be totally illegal since you will not have committed any crime (guidelines being optional to follow) and again, they would not be enforcing any law.
Know the difference: Guidelines come under 'civil law' and crimes come under 'criminal law'. The police are not allowed to enforce 'civil law' - only the local authority and the civil courts can attempt to do that. So, demand that the Court issue you with a date for an appearance, and when/if you go to court your defence will be illegal detention and kidnapping, and in the civil court you will be able to demand substantial compensation as a counter-claim from the police, plus insist that criminal charges are brought against the arresting and detaining officers.
Now, nobody says that it will get to that stage, indeed it would be very unlikely to, but can you imagine how the Courts will be clogged up for years, perhaps decades, trying to process those bloody awkward bastards who had the bald-faced cheek to know the Law and also know their civil rights.
PS: Ensure you use your phone and record the whole even, to be used as leverage and evidence. But just remember this one fact - the police cannot enforce civil Law and therefore have no rights in determining whether or not you have to wear a mask, just because the government says so. That process would be called a 'dictatorship' and we are not quite there yet, despite this government's valiant attempts to make it so.