Incidentally, I don't think that any Army, local authority or RAF fire appliances can meet the requirements for CAT 9 fire cover, which is what would be required at Heathrow and Gatwick.
Crash CAT 9 isn't that hard to cover for a couple of airports.. RAF Brize Norton is Crash CAT 7 and most other RAF Airfields are around Crash CAT 5 so to combine some units would be possible.
I wonder just what percentage of BAA Security staff are Unite members..