why is there nothing in the inventory now capable of STOL or carrier operations ?
Because the Navy, in collusion with Gordon Brown, contrived to make the carriers un-cancellable through devious contract-writing. New government rightly annoyed by being forced to continue with the carriers regardless of outcome of SDSR. Decides no point chucking good money (i.e. GR4 ability to conduct simultaneous HERRICK and contingent ops) after bad.
The Navy have been hoist by their own petard, I would say.