BHX main problem at present is that we have 9 stored Ryan Air 737s blocking out a lot of our remotes.
Assuming they're not parking for free, is that really a problem? No one is going to be weighing a "no" to a diversion ages ago when weighing up a decision to start a new route, come on guys let's be realisitic. Diversions are nice for enthusiasts and a massive pain for everyone else.
Passengers, crews and aircraft all in the wrong place with the potential for coaching for all and hotels requiered. To be honest, that's a hassle a handling agent will not welcome on any given day. It's easier for a third party handler to refuse a diversion than in house staff. There are of course, no in-house staff nowadays in UK handling outside the major bases of BA and Jet2. (Anyone think of more? )