Join Date: Oct 2006
Location: London, UK
Programs: BA Gold, VS Silver, SQ Silver, IHG Plat Amb, Hilton Gold, Marriott Plat, Accor Silver, Radisson Prem
Posts: 16,871
In answer to 1) there is only one security central security check at all LHR terminals, although there may be random checks at the boarding gate.
In answer to 2) the official customs desks are best - there is one landside in check-in (at the front of the terminal on the plaza), and one airside by duty free, just after central security.