@peterdutoit From Cambridge, I can get a train to Stansted and then a budget airline flight to a load of places in Europe for far less than the cost of a train to most parts of England, and certainly for less than a train to Wales or Scotland.
Last time I went to Edinburgh, I got the train, but a standard-class ticket was more expensive than flying. This was quite a few years ago and the train price has gone up a lot since then. The cost of the flights has gone up slightly. The train and plane take about the same time once you factor in the waiting time at the airport and the need to get from Edinburgh airport to the city centre.
When I moved here from Swansea, if I went back on off-peak trains it was £33 standard class and £44 first class. First class was comfortable and I could work on the train. It also came with free drinks and snacks, so worked out about the same price. I went to Newport last year (about two thirds of the way to Swansea) and it cost a bit over £100 for the same trip. Flying to the south of France on RyanAir is cheaper than that.
Great Western’s first class remains the same quality but a lot of the other rail operators are much worse. Standard-class seats that will cause back pain if you sit in them for more than a short trip and first class that’s basically the same.