London Gatwick Airport

Gatwick is a major airport south from London used by low budget airlines such as Jetstar, Ryanair and Easyjet.

Towards Dover, London, Brighton
Outside of the entrance to the airport road, past the McD's, is a large roundabout. You can flag down people coming out of the airport, or if you feel like trying your luck on the motorway (technically illegal) there is space to pull over. If you don't feel safe crossing over the road, 200 metres east of the roundabout is a road that passes under the motorway. If you want to walk a mile, once you have passed under the motorway (see above) there is a muddy little path that runs parallel to the highway. Follow this three quarters of a mile to the next roundabout, where the M23 turns north. Hitchhiking on motorway ramps is legal, and just after the ramp is ample space to pull over.

If you're heading towards Dover you should ask your driver if they can take a detour to the and drop you off at the service station Clacket Lane Services north.

If headed South towards Brighton your best services to aim for if not able to get the whole way is Pease Pottage

Freebies:

Almost all throughout the airport there is free wireless. It's called Wifi-Zone The Cloud

Sleep
It is possible to sleep in the 'landside' part of both South and North Terminals. Plenty of aircraft travelers who have had their flights delayed/cancelled sleep on or under the chairs dotted around the terminals. The North and South terminals are connected via a free shuttle mono rail.