Not sure about the UK, but in the US you can get a bank account and debit card when your parents co-sign as early as age 14 (Bank of America). Is age something merchants get back from Visa/MC when you make a transaction?
Something like that could be used to filter out such cards, if they were assigned a unique BIN by the bank. As to whether anyone actually _does_ that, I don't know.
[1] The BIN is the first six digits of your card number. It identifies the originating bank, among other things: https://www.investopedia.com/terms/b/bank-identification-num...
Even though a debit card acts like a credit card under most circumstances where your available balance is effectively your "credit" limit but there are ways of telling the difference between a debit/check card and a real credit card.