My chosen method of travelling to and from London yesterday was via National Express - a coach company. While coaches take longer to reach London than trains do, they are significantly cheaper. Once I knew when I'd be travelling to London, I booked a month and a half in advance and paid a low fare for my tickets; the other trade-off besides the journey taking longer is that I was restricted to taking the buses at the specified booking times. For example, my bus from Nottingham was only the one at 6:05am and my return from London was at 9:30pm; if I'd missed them I'd have to have bought a new ticket for another bus and it would have been more expensive.
The route down was fun. While much of it took place on the M1 (the UK's main motorway from the south to the north), there was a brief stop in Milton Keynes and the route through London to the Victoria coach station took the bus through the Royal Borough of Kensington, which I'd never seen in person before. For the route back, it again stopped briefly in Milton Keynes but also went through downtown Leicester, which makes it the second time I've seen Leicester between 12:00am and 2:00am.
Will I travel via National Express again. Most certainly, yes!