The old services to LHR back in the 1980's were with Air UK on their Shorts 360's. The flight actually routed via NWI, though towards the end of it's life I think the NWI stage was dropped and it became non-stop.
As for Eastern's pax loads on HUY-ABZ, they actually average around 15-20 on each flight and attracts significantly more passengers than their LBA-ABZ. I know as I used to work for T3 and saw the pax figures for every flight. Probably still not enough to warrant a FlyBe service but just wanted to let people know that loads are ok on the route.