Aye, six of us.
Taxi would be about £80, but won't be an issue to get one (if you get out of the immediate vacinity of the ground, towards the city centre).
Train is £12.50 off-peak, most take slightly under an hour. Last train is just after midnight.
Bus varies in price, but probably around a fiver. Again, last bus is midnight. Book it online at www.megabus.com.