Are you quite sure you know what's going on IN the UK???
Not everything. We all know things go on that area, drugs, money laundering, organised prostitution - all -
illegal, e.g. young women transported to the UK from Eastern European countries for the purpose of prostitution. Plenty of other things that are illegal. Tht's the point, the illegality. If it is uncovered, people are prosecuted. Doesn't all happen overnight.
No idea what you are getting at precisely.There are no legal marriages of children here. Go back to the 12/13th centuries, children were married to other children, generally noble-folk, one woman I read about some time ago was widowed twice by the time she was 13! A few years later she contracted a marriage with someone she loved, had children and lived happily for many years but she had still been 'married' at the age of 6 to a little boy. They lived in eachother's houses, played, took lessons etc. like other kids. The parents had arranged the marriages, with the intention of uniting noble houses.
That wouldn't happen now but illegal stuff still goes on. I've not heard of 'child brides' in UK being that common though, might happen but certainly illegal. Happens in other countries especially remote areas - Plan UK is good charity to support that helps stop this sort of thing.