Apologies. It’s just that people keep saying “oh but we have them, surely you do”?
But the only government issued ID in the U.K. are a passport and driving licence.
Both those you mention are valid within the U.K., for things like proving age for buying alcohol, although no one is forced to accept them, mainly because they are easy to alter (and plenty of 16&17 year olds have either altered one or used someone else’s). And they cannot be used as official ID for anything. If you don’t have one of the two official IDs, you have to jump through hoops, with birth certificates, different proofs of address and soon to open a bank account or anything.
My own kids both applied for a provisional driving licence at 18, to make it easier to prove their age at a bar or shop. But that on it’s own is not even accepted as official ID, although Disney accepted them.