Why omfg Norah? What is wrong with wanting to know exactly what the legislation or not is? If I am told something, or refused something, then I want to know exactly where I and the other person stand in law. If the law is inconsistent as it seems to be in this case with differing councils according to you setting different rules, then how is the consumer supposed to know what those rules are for different areas?
Yes, it's a shitty system, and I'm sorry for the cashiers, but please remember that if the consumer didn't buy alcohol, or patronise your establishment for other groceries, then the profits of your employer would fall, and redundancies could be made. It only takes one bad experience for someone not to use a shop again, and at the moment, I would have thought that the shops would be pleased to have customers.
The system needs to be crystal clear right across the UK so that there are no misunderstandings. That is obviously not the case at the moment, so we are trying to establish what the law is, as opposed to what the retailers decide to do, and if what the retailers are doing actually has the force of law. If not, then one could argue that they are being discriminatory in not selling to people because of their appearance or inability to drive, or that they have no ID, which is not a legal requirement in the UK.
Perhaps you'd like to point out to your employers that the system isn't working, and how they could ameliorate it, so that Joe Public can understand it clearly.