For early departures, of which there are many from Gatwick, it is definitely worth staying overnight in a hotel near the airport. The journey from London takes a long time and although trains run 24 hours a day, staying near the terminals will definitely be more pleasant.
Hotels near the terminal (5 min. walk)
There are several hotels in the immediate vicinity of both the North and South terminals, from which you can walk to check-in in 5 minutes.
South Terminal
North Terminal
The average price per night for two is around 100 gbp when booked well in advance.
Hotels in the area
Significantly cheaper hotels can be found within a perimeter of about 5 km. None of the nearby hotels offer a free transfer to the terminal, so choose from those served by the special Gatwick Hoppa airport hotel buses (see details). The fare is 3 gbp per ride (payable in cash at the driver's desk or also at the hotel reception).
Traditionally the cheapest hotels include the Holiday Inn Gatwick or Travelodge with prices around 80 gbp per night.
Hotels in London
If you don't mind travelling straight into the city at night, choose from a much wider range of central accommodation.