Sounds painful, especially when you can get a flight for less than £30 - admittedly this would probably require a train journey at both ends but then again I don't suppose the coach will be picking you up outside your house and dropping you off at The Valley! It's OK trying to do things on the cheap but you have to consider your sanity as well!
I wouldn't worry mate, I lost my sanity a long time ago! As I'm sure a few posters on here can verify Costs about £6 return from mine in to Glasgow so that's £28.50 then whatever else on top once I get to London. Certainly works out cheaper than train or car! Megabus do "sleeper services" - £45 each way, pfft.