Airports: book ahead
Start with airport hotels, which sorts every terminal by the rule it follows. Heathrow breaks down into Terminal 5, Terminals 2 and 3 and Terminal 4; Gatwick covers the North and South Terminals. Both airports set a floor of three hours, travel time included, and the taxi is folded into a single total. London City is the exception: one hour upwards, with a Zone 3 fare added.