Brighton is one of England's best seaside towns. It is about an hour by train from London (Victoria or London Bridge stations) and 40 minutes from London's Gatwick Airport. It has a very active sex scene (gay and straight). It is very busy during the main holiday season but OK outside these times. Parking is a real pain in the neck so I would suggest going by train.
There are lots of free-lance girls and a few parlors (try Brighton Belles or Foxy Ladies, both near the pier) where you can find entertainment. Check the adultwork site (southeast/east sussex) and Friday-ad site (search Brighton/Adult).
Some of the ladies in Brighton will do outcalls to Gatwick, so if you are stuck there overnight and don't want to go to Brighton, give them a calls but you will find more Gatwick outcalls under 'West Sussex'.
Brighton is well worth a visit anyway but as there is lots of action there, even more so!