I always look at http://www.splityourticket.co.uk/ or http://www.moneysavingexpert.com/split-cheap-train-tickets/
Its often cheaper to buy split tickets on the same route A-C-D-B than just A-B, you can still be sat on the same trains except rather than a return from Brighton to victoria, you...
youve got to be kidding, for less than a quid you put an envelope in a red rural post box in sussex and it ends up in a front door on an estate in Edinburgh in under 48 hours?
how much would that cost you to take yourself?