The UK CAA do virtually no enforcement. Most (not all) of their prosecutions are cases where somebody was blatently taking the micky. One or two are of people who p*ssed them off in previous years (the police do the same).
There is a lot of stuff the CAA could enforce but they choose not to - presumably because the vague wording of the ANO (and its many and varied interpretations on pilot forums
) suits them. They do not want to test a lot of that stuff and end up with a precedent which would open the floodgates.
The FAA (in the USA) is pretty heavy in comparison.