if bmi still has spare LHR slots this summer then putting up a couple of flights per day on the route BFS-LHR is maybe their best bet?
They're known in Belfast but perhaps feel they can target a slightly different market with BFS rather than BHD. Plus, if they do still have LHR slots spare, this is perhaps a better bet than throwing additional frequency onto LHR-MAN, LHR-GLA or LHR-EDI..