I would agree with Catflaps, that if there is a valid S106 agreement in force then it has to be obeyed by whoever owns the airport. What I haven't done is check whether there is a valid S106 in the first place.
Irrespective the airport owner would be wise to try and keep in with the local authority and provide reasonable information they request particularly if the owner already has it!
The real question I have is if the airport is dead on its feet and has no traffic why have the complaints gone up so much? Surely you need flights to generate the complaints?