I don't think there's any reason to think some special efforts were made to faciliate the arrest...
GL was on an American Airlines flight so hard to see the Met having clout to bump him off that onto a preferable one, though I guess not impossible.
Further anyone arrested airside at most airports, certainly at LHR, will be confronted with armed police since the unit that is based at and covers the airport is an armed one (due terrorist threat to airports, etc).
There would certainly be no need for extra time being needed to organise a team for GL's flight, they are available pretty much instantly, often seen walking/driving around the airport on any normal day.
The one question still worth asking is exactly who ordered arrest at the aircraft side...what followed at Heathrow was a consequence of that single decision.