Disregarding Siam for now, I have to agree with fluffy that there is a lot of nonsense goes on in the UK, particularly "private flights" that are clearly charter being one of the biggest, often flown by PPL's who sometimes wear 4 bars for added effect.
Everyone knows its happening but it doesn't seem to get any better, as I understand the CAA's position you have to provide them with proof rather than allegations as they don't have the capacity or willingness to investigate.
A CAA guy once told me about a "charter" he witnessed about to depart battersea, as the pilot with 4 bars was helping the pax get on board, he thought he should ask him a few questions, it turned out he was not only a PPL but had an expired LPC, this type of thing goes on all the time unfortunately