Originally Posted by
UAPremExecflyer
Follow the sign for "Flight Connections". When you get to immigration/security, stay to the left and you will go through a passport check and re-screening. You will end up in the main *A departures area, with transfer desks (including TAP).
One correction: there is no immigration check to clear when going through LHR connecting to an international destination (besides Ireland).
Originally Posted by
teflon
Coming from Gatwick, this means buying a single ticket from the airport to the first station inside the London fare zones (Coulsdon South - it should be £5.70).
A ticket to Coulsdon South plus a zone 1-6 ticket valid for less than a week will only be valid on a train that stops at Coulsdon South. To use a fast train a ticket to Boundary Zone 6 is required. This probably costs more or less the same, although it can only be bought from a ticket window.