Are you allowed to show in your film kids or teens drinking alcoholic drinks? Or is it against the law in the UK?
As far as I know it isn't illegal in the UK to have under 18s ACT drinking alcoholic drinks, ensuring you are giving them non-alcoholic drinks. For most acting, actors will drink a non-alcoholic substance that looks like beer, since we wouldn't want drunk actors.
On the 8/6/16 in a Soap known as Coronation Street a 16/17 (I can't remember which) year old boy had a hangover which you get from drinking too much. On the 6/6/16 he was handing beer (while near 2 adults) and at the end of the scene he takes a couple of bottles after being denied some beer to drink. There have been other instances in the soap where kids have been drinking or attempting to. So it's legal to have kids acting drunk or acting to drink so long as you give them non-alcoholic substances.