The perm hex code in the mode S transponder is linked to the registered owner and Reg.
Technically that is true but I gather that UK ATC do not have access to the database which does the Mode S code to the aircraft operator conversion.
It would be funny if they replied to V. pilots with "Good Morning Mr Branson, where would you like to go today"
Of course, how else would their computer know where to send the bills? (which is their motivation for Mode S)
That is
AFAIK not the way it works in Europe. A good number (IIRC) of European countries have no interest in Mode S and don't require it in their airspace. The Eurocontrol IFR enroute billing (> 1999kg) is done by a unit which runs a database of aircraft regs (tail numbers
) and maintains a correspondence/billing address for each one. For foreign reg planes, that process will be very haphazard because the tail number does not lead to the aircraft owner; the bill instead goes to the US trustee who then sends it onto the operator with a stroppy letter, and this encourages the operator to contact Eurocontrol and update his details.
I dare say Eurocontrol have a lot of fun chasing after the more elusive planes... I wonder if they refuse to accept a flight plan for somebody who has not paid the bill? Could be quite a problem if you bought a used plane which is over 2T.