Yeh I'm thinking I should ASAP. Infact as it's from Euston, no changes, shouldn't everyone coming from London? So this is definitely going to happen, 20th Dec? Last weekend before Xmas, might have to work is the only problem.. hmmmmmmmmmmmmm
EDIT: Its on the National Rail website. I searched for London (all stations) to Liverpool (all stations) on 20th Dec and returning on 21st Dec. With a 16-25 rail card (which only takes 1/3 off so it should still be quite cheap if you don't have one). The advance fares are like £5- £10 each way depending on which times you travel.