It's worth having a look at the CAA stats to gain an understanding.
BHD-LGW is some 6,000 higher in Oct compared to last year. Add to that nearly 4,000 pax that flew BHD-LTN with limited impact on BFS-LTN. Between FR + U2 there's an additional 20,000 on STN. There's also growth on BHD-LCY over 3,000.
All this can't be just pure growth, BHD-LHR has took a hit and, needless to say so has BFS-LGW. It comes to January and fighting to fill aircraft that you'll not likely to succeed at just isn't worth it. If you look across the airports U2 have a huge schedule to London and having flexibility on where you take off and land from is key to getting a good price.
I'd just kinda put to bed the notion of the shuttle service schedule of the 80's/90's. This is low cost carrier territory now, even BA have chopped away heavily on frequency.