London Stansted Airport
Stansted Airport is the king of econonomy airports. Ryanair run to more destinations from here than any other UK airport. Easyjet also have Stansted as one of their major hubs. Several other budget and charter airlines also run from here. The building itself is a giant hangar-type affair, with kiosk-type buildings for all the shops and single storey walls separating the flight-side and check-in areas. The overall effect is of a pleasant open terminal which is larger than it really is. A good range of shops and cafes is available, although prices are at the usual fairly-astronomical levels you find in all UK airports. The gates are mostly connected to the main terminal by a transit system, meaning that once you get to them there is no turning back, and since there is only a coffee stall and seating at the gates you probably don't want to head there too early. Between the absolute 40 minute cut-off for most budget airlines, the transit to the gates and the possible queues at security, you should aim to arrive in plenty of time.
Getting there on foot
Stansted Airport is fairly close to Stansted itself, but Stansted is quite small and more difficult to get to than the airport. Face facts - you're just going to have to pay for the train.