I keep hearing that people are paying silly prices to get to places to ride, use megabus.com you can either get the coach OR use the trainline, basically it offers really good prices off peak, which are where the rides usually are on a Sunday theres usually loads of tickets free, e.g. John Mack just said he was interested in trying to get out on a ride with me soon, nationalrail quoted me £50 for a ticket from Bristol - London. At megabus the same ticket is only £1-3 single with a 50p total booking fee on your order.
The only problem is you have to buy singles, e.g. when I went to Leicester from Portsmouth I brought 4 tickets like portsmouth -> London, London --> Leicester and payed for the underground by myself but in doing so saved over £20.
They accept NUS cards as a student rail card discount also. Winner. Check it out.