Originally Posted by
gardengirl
To make the day more interesting, would it be advisable to split the time exploring both T3 and T5? I'm also wondering about splurging on Elemis Spa. Usually I'm too frugal (cheap) to do much of this but trying to make this long layover part of the vacation experience.
LHR cannot entertain you for eleven hours.
If you can entertain yourself for that long, find a quiet spot in a lounge. Otherwise, go to Windsor or London. Many museums in the UK are free to enter, particularly in London, and public transport from T5 to South Kensington is, as
Microwave suggests, cheap, safe and easy.
Heathrow discourages entering into the wrong terminal. It is possible [except T5] if you are insistent but staff will assume that you are lost. You may also be denied lounge access except in the departure terminal.