I am in the UK too.
I have noticed normal blue top "whole milk" varies in fat content from 3.1% all the way up to 4.2% depending on which dairy it is from.
Organic milk tends to make up the higher end of that scale.
And Jersey, non-homogenised milk contains about 5.8% fat.
I have found that better tasting/better quality milk tends to have higher fat.
Same goes for yoghurt, low fat is kinda sour/sharp, but higher fat types like greek yoghurt are delicious.