Transport Gatwick

http://www.gatwick-airport-guide.co.uk/london.html#b

Coaches to London

National Express

Buses depart from Gatwick to London Victoria Station once per hour. The journey takes about 90 minutes and single tickets are available from £6.60.
To make sure you dont miss your plane, National Express advise that you plan ot arrive at the airport 1 hour before check-in. You are able ot take your luggage on the coach, however, as with airline travel there is a 20kg weight limit.

It is worth booking in advance as National Express have removed the booking fee when purchasing your tickets online.

Hotel Transfer

Direct hotel transfers between Gatwick Airport and Gatwick Airport hotels are offered by National Express.
National Express coaches depart every few minutes at peak times from outside the North Terminal arrivals and South Terminal arrivals, offering convenient access to Gatwick Airport hotels. The services serves Ibis Gatwick Hotel, Crown Plaza Gatwick, Ramada Plaza Gatwick and Travelodge Gatwick Airport. Prices start at just £3 for an adult and £2 for a child if booked in advance.

Buses Around London

Most buses around London are low floor, meaning that they lower to pavement level, making it easier to board the bus. You are now able to use Oyster cards on bus routes.

For more information on what buses to get and timetables for the buses, visit Transport for London.

Trains

London Victoria

Gatwick Express trains run every 15 minutes and the journey time is 30 minutes (35 minutes on Sunday). Standard tickets cost £16.90 single and £28.80 return. For more information, please call +44 (0)845 850 1530.
Southern service to London Victoria takes about 35 minutes and costs £10.90 one way. Trains run every 15 minutes during the day and every hour at night. (Please note that the times may vary in the first and the last hour of the day). For more information, please call Southern Customer Support on +44 (0)845 127 2920.

London Bridge / St Pancras

First Capital Connect trains run through London Bridge, Blackfriars, City Thameslink, Farringdon and St Pancras stations to St Albans, Luton and Bedford. There are four trains an hour during the day. The journey to St Pancras takes 45 minutes and tickets cost £10.90 one way. Please call First Capital Connect Customer Relations on +44 (0)845 026 4700 for more information.
http://www.firstcapitalconnect.co.uk/static/pdf/network_route_map.pdf

What child fares are available?

Children aged 5 to 15 travel at half the adult fare. Children under 5 can travel for free (this does mean though that they are not entitled to a seat and therefore if a service is busy you are expected to travel with your child on your lap). http://www.firstcapitalconnect.co.uk/customer-care/faqs/search/