The solution is
to also buy a single ticket from the train station immediately before your destination to your destination station, and show that ticket when you get off. Costs a couple of quid extra, but no hassle.
(Mystery_Machine, Wed 16 Nov 2011, 8:59, 1 reply)

Can you do that online as well?

( Je suis un vagabond is an unfunny, up your own arse middle class knob, Wed 16 Nov 2011, 9:46, closed)

I think you can actually
It's interesting, have a play on the national rail website. Look at tickets from where you live to places in Ireland and NI. NI approved routes go via Scotland from Sussex. You'll find it's much cheaper to get the Ireland / NI tickets and you can simply buy Glasgow Airport to Glasgow Central ticket £2.90 as your get out of jail free card. You could even buy this from a conductor.
(sunray18, Wed 16 Nov 2011, 11:00, closed)

It's also worth
breaking your journey up where you change trains. I'm travelling from London on Sunday, and by buying a ticket to Crewe, then a ticket to Bangor, I'll save about £30.
( social hand grenade I was a lurker before you were a lurker, Wed 16 Nov 2011, 20:36, closed)