JFD, I would have to agree with you with respect to your theory regarding heavy maint. disappearing abroad. BA have already done that with their 747/777 fleet in BAMC Cardiff & 737/airbus series fleets in Glasgow. OK it might not be China but the land & labour costs are far cheaper than at Heathrow & Gatwick.
Funny how the Beancounters didn't seem to worry to much about cost when BA built its new HQ 'Waterworld' with its indoor babbling brook running over the imported Spanish pebbles ( B&Q wasn't good enough ) & not forgetting the cafes, a little Waitrose food store, a newsagent, bank, a hairdresser, a library, art gallery and so on.
Our tight arse management can't even supply us with basic hand tools like a sodding 3/8" ratchet ring when mine gets pinched.