Easybus.co.uk (part of Easyjet) has a Bus service from London Central to London Luton Airport - starting from just £2 each way.
National Express charges £15 each way !!!
London Luton is the home of Easyjet and this special bus service is to lure customers to Luton, who otherwise avoid it.
You must print off the booking confirmation to show the driver. If you do not have a print out of the booking details with the confirmation number to show the driver , you will be required to make a new booking at the walk up fare price.