Not sure what supermarket you are referring to above but no supermarket here sells alcohol that I am aware of. There are however designated “booze shops” (many adjacent to supermarkets such as Spinneys) that sell alcohol to license holders (only available to residents) - some will sell without checking for a license. Visitors also technically need a license to drink in hotels (even if they are staying at that hotel) but its rarely enforced unless one draws attention to oneself.
My reference to the supermarket is in regards the kitchen, and the fact you can prepare a private meal rather than rely on the restaurants. I was quite surprised how cheap the beef was, anyone not happy with the supplied dinner or staying over the weekend could quite easily cook a decent meal with little effort.