I can get to/from London on the 10th Dec for under £40, early start/late finish - well I could if I wasn't going to watch my beloved Leicester City play Man City on that day.
On the 17th, there are no cheap 'Advance' fares; the minimum I can find is £86 return from Chesterfield. If I drive to Nottingham (i.e. closer to London), the price jumps to £120 return?
The Advance fares appear to stop on Fri Dec 16th. If I was being cynical, it looks like they have stopped cheaper advance fares just before a rush for Christmas bookings as people try to get home or do last minute big city shopping. As much as I love travelling by train (and I could probably do without driving after exiting/entering multiple tube stations), I'll drive to save money.