BMI have pretty much got the airport where they want them here.
If LBA agrees to lower the charges then the route will probably survive a little longer.
If LBA play "hardball" then BMI walk away and say "we tried but LBA didn't want to know".
Ultimately it's about the most profitable use of that most scarce of resources - LHR slots - and if BMI think they can use them more profitably elsewhere then it's game over for LBA-LHR.
As Spanish Flea stated here (& I said similarly on BLK thread earlier!) the shorter air routes to London are increasingly under threat from a superior frequency of train services. Outside of MAN I doubt they will last until 2020 if / when the 3rd runway appears at LHR.
However, there are bound to be other markets that will open up over the next few years - one door closes, another one opens!!