Moderator: American AAdvantage, Signatures
Join Date: Jan 2008
Location: London, England
Programs: UA 1K, Hilton Diamond, IHG Diamond Ambassador, National Exec, AA EXP Emeritus
Posts: 9,795
I would definitely suggest taking the airside transfer option, unless there's another reason to go landside. In addition to queues at immigration, there can also be complications for certain nationalities gaining entrance to the UK which can be obviated by staying airside at Heathrow. Good luck!