Yes; there have been multiple threads in the bizjet forum and elsewhere saying how the CAA goes after these ops but always settles on the court steps. It may be hearsay but it is quite persistent.
I am sure they don't want to create case law on scenarios like the one where the aircraft owner writes two cheques (one for the pilot and one for the leasing company) but the pilot has actually arranged the whole lot. There is no doubt IMHO the CAA would lose that one.
And let's face it - who cares? It's hardly carrying unsuspecting paying passengers, like the CAA's "illegal charter" leaflet says.