Upvote:11
There are three stations:
(Note that 2, 3, 4 and 5 are the only terminals: TerminalΒ 1 closed a few years ago.)
The station for Terminals 2 andΒ 3 is between the two terminals and is reached by clearly signposted pedestrian tunnels. The stations for 4 andΒ 5 are in the corresponding terminal and, again, clearly signposted.
There is more information on the airport website.
Upvote:21
The tube or subway is called the Underground. A typical direction sign within a terminal at Heathrow is shown below.
The London Underground logo is used everywhere in the signage.