Depends how much train travelling you're planning to do Mrs.Lamps.
The lads I'm with are all planning to get a "Eurodomino" railcard, because we'll be getting from, and then back to the airport by train, aswell as scooting about during the week to a few different cities.
The pass lets you have unlimited rail travel on a specified amount of days of your choice during a rolling month period (i.e. 5 days during the month, any distance per journey - £170)
Damn site frikkin cheaper than UK rail too!
Here's a link to some prices etc that we found:
http://www.raileurope.co.uk/railpasses/eurodomino.htm
Hope that helps...