More proof needed please on people who eat anything stating 'people of the book'.

One of the main issues we have here in the UK with this is that the butcher of the meat themselves needs to be known as being from the people of the book, meaning from the Jewish faith or the Christian faith, and also there's a particular way in which they need to slaughter the animal and so on. Here in the UK there are a huge percentage of people who have no faith and there's no way of verifying what the faith of the butcher was or how they slaughtered the meat and so on. Because of this it's not permissible here in the UK to eat from meat which has not been mentioned that it has been slaughtered halal.