Non-stop flights from London Heathrow to Miami start at about £400pp, or you can get lower fares if you are prepared to make one or two stops en route. Expect higher prices around major holidays.
Rent a car in Miami for the 90-minute to two-hour drive (depending on your destination in the Keys and traffic), or hop on a short flight from Miami to Marathon or Key West.
Plan your sightseeing and meal stops geographically or you’ll waste precious time driving unnecessarily. Street signs along US – the only road in and out – consist of mile markers (MM). Those, and the designation ‘bayside/gulfside’ or ‘oceanside, are all you’ll need to find most places. For example, if you want to stop at the Islamorada Fish Company for lunch, look for MM81.5/bayside, in Islamorada. Most visitors – especially young ones – find this fun, once they get the hang of it.