but why didn't they make it simple?
HMRC think it is! Sadly they don't always fully understand how things operate at the pointy end.
Collection should have been put to the airports who in turn place the responsibility on the handler along with collecting Landing, Nav & other PAX charges as most currently do.
Simples!
So in fact the FBO needs to check fiscal backgrounds etc of an operator ?
Roughly speaking yes. More specifically the OPR's registration and any Fiscal Representation however this wont necessarily protect them, especially from any rogue operators.
I have asked a few Q's of HMRC re the effect on FBO's and await their reply.
Stand down. Outbreak of common sense @HMRC: Handlers will get notice prior being made liable for FUTURE duty & it is NOT RETROSPECTIVE.
As you were!