Fair enough, you've earned an honest answer! lol Had you said this year you'd have been hounded from the forum 
292 miles on foot, if you averaged 11 m/m 26.5 hrs, if you plan on doing this everyday, I'd suggest maybe running 3 hrs a day? That would be 9 days. you can do it quicker if you want, but obviously the less time you give yourself, the less likely you'll be to make the start line in London, plus even giving yourself a years full training will still make you a novice for even a single marathon, let alone what you're considering.
As for training, that depends entirely on what you're already doing, and what you're capable of without training, no one can help you unless they know what they're starting with. Surfing, skate boarding, baskbetball, boxing and recently squash wont really help you much unless they've kept your weight down, which I'm assuming they do.
Get outside and assess your running fitness, run slowly, and see how far you can run without pain. Then come back to the forum 
Edited: 03/03/2013 at 01:43