Everything depends on the venue. Unless someone here has been to the venue before, they can't say. Although there are national laws, different venues have different licenses and also differing stances on strict/not so strict adherence to the rules. For instance, I've been turned away from a couple of venues in London for not being 18. I've also been to many that state "Only over 18s. Anyone underage will not be admitted" but don't ever ID people. If I go to a venue that's 14/16+, I'm usually alright, but once my friends got IDed at the Garage, which is only 14+ and we're all 17 or 18 just because they're getting really, really strict there.