Chiltern?
None of this Virgin hassle about having to book bikes, and I think advance singles are £5, walk up off-peak fares £25 or less if you've got a railcard.
Edit:
London Midland are even cheaper, but you do need to exercise some patience ( l-o-n-g journey... )
Prior experience suggests that Virgin is infinitely preferable for getting back after a FNRttC, as both Chiltern and London Midland take forever, and mean sitting on the uncomfortable fold-down seats by the bike spaces, being constantly woken by people asking if there's an idiot who doesn't understand the door controls in the toilet. By the time I get across London I'm thoroughly knackered, and an hours snooze on a half-decent seat in the quiet coach (with minimal poo smell and the bike safely away from meddlers) wins hands-down.
I'll happily use London Midland after an overnight ride *to* London. I'm less exhausted at that point.
Virgin bike hassle can be mitigated by use of the eastcoast website to book bike spaces at the same time as advance tickets, and pirate carriage keys provide a form of insurance against failure of train managers to appear to open the door.
Luckily I've managed to get the fare down to something relatively sane by splitting the ticket at London (usually it works out much cheaper not to, at which point it becomes a question of how quickly I can wheel a bike through the crowd at Victoria and ride to Euston), but they seem to have stopped doing bike reservations on the Bognor-Victoria train.
And I should now be on the list...
