Introduced in November 2007 dot2dot is an airport door to door shuttle bus service operating into and out of central London to Gatwick and Heathrow airports, thought not between the two airports themselves. Services operate into central and east London as far as Canary Wharf.
Formerly a division of National Express the company uses a sophisticated website and integrated technology provided by Microsoft to match passengers to destinations. National express also bought out an existing shuttle service, Hotelink, and have rebranded that service under the Dot2Dot brand. Its a shared shuttle service and while you can pre-book via the website (best chance of obtaining availability) you can also simply turn up at their desk in each terminal. The service runs 24/7.
 
Safety seats for children provided (3 years and up, if under 3 the child must sit on your lap).
Also special needs can be catered for (pleaser provide 48 hours advance notice).

The fleet consists of 12 seater custom built buses with climate control. They are fitted with all age seat belts.
For pickups from London the company will allocate you a 15 minute window at which time you need to be ready to leave. Unlike a taxi service they cannot give unlimited waiting time to their customers at pickup addresses. The driver will assist you with baggage. The shuttle service drops you at your appropriate terminal. There's 5 terminals at Heathrow and 2 at Gatwick.
For airport pickups it works slightly different depending on where you arrive. At Gatwick a uniformed Dot2Dot representative will meet you as you enter the arrivals hall with your name on a board. At Heathrow you need to make your way to their desk in the arrivals hall. Their policy is to try and have you on  bus within 30 minutes.