I've been assured that it's a temporary issue. More airbridges are being built, in fact there is one being put in directly above the bus loading area. The difficulty is that building in any airport is tricky, building in an airport that spends months in darkness in dreadful weather makes any project a fairly long term undertaking. It's been buses since almost the start of the service. BA pays no more, no less for airbridges or buses, it's part of the airport's logistics service.