I regularly do a 1 hour train journey / 1.5 -2 hr drive in to London on a busy commuter route, and the peak train fare for 1 person inc travelcard is £47 to get delays and stand like sardines. A taxi would be circa £65. Train companies need to sort themselves out. If a taxi in rush hour was slightly quicker I'd get the taxi instead for the extra £18.
I've had a look at a couple of websites trying to figure out exactly what is/is not possible in the days after Christmas. I like to think I'm reasonably intelligent and I can't make sense of any of it! They've made it so difficult that I wonder if it wouldn't have been better to close the whole network for 3 or 4 days and just get it done quicker!