As Crocit hasn't replied, i'll mention my thoughts!
The main problem is that there isn't really a train back after the match. If you can find a way of getting home, then book your train from virgintrains.com and you should get one for the way there pretty cheaply, though the prices are going up. One option to come home is a coach, N.E., but that'll be an overnight job, so a better bet would be to get the T.C. coach both ways, but it's a pretty long haul! Alternatively, my preferred option, get a cheap train there, stay in a cheap hostel for the night (<£20) and have some beers in liverpool, a good night out, then get a cheap train back to london in the morning. Sorry i don't have any magic answers though!