They don’t have fluoride in the tap water in the UK. That’s one of the main reasons their teeth are universally terrible.
I was born on the High Plains and Ogallala Aquifer well water was my drink till I was 8 years old.
Then it was 4-Corners Alkalai water with natural fluoride.
I am now 75 years old and I, my brother and sister still have all our teeth.
My mom, on the other hand, was born and raised on well water in Tennessee. Natural limestone well water.
She had to have all her teeth capped as a teen and finally got dentures.
Dad died with all his teeth as he was also raised on a little bit of Ogallala aquifer well water, and lots of beer and whiskey.