You could try megatrain from Glasgow to Birmingham and then an advanced from Birmingham to London. Might save some money over the advanced through ticket.
I am wanting to travel late june,from glasgow or edinburgh to london,anytimes.
If you are quick you may get one of the East Coast £12 specials but you have to book by midnight tomorrow (there is a link on here under the online offers thread at the top)
http://www.eastcoast.co.uk/special-offers/may-2012/48-hour-flash-deal/
that one to be precise
Nice one,will be trying that option,ta much