I am not sure about the stats in the UK particularly but the "consanguinity rate" per capita wise is a lot higher in the middle east.

"The consanguinity rate in the UAE has increased from 39% to 50.5% in one generation."

From what I have learned, it has a lot to do with "wealth preservation". Something important I guess if you are a millionaire sheikh and get regular allowances from the ruling royal family according to your family title/name.