I (32f) recently got a train across the UK from London to Aberdeen. It's a seven-hour journey so I booked myself a first-class seat well in advance. First-class seats on trains in the UK can be expensive, but I decided to treat myself because:
1. I was making the journey the day after returning from a two-week-long work trip abroad and I knew I'd be exhausted/ totally unable to function.
2. I knew I'd have work to do on the train, so I wanted to make sure I had space/ comfort to be able to work.
3. On certain trains in the UK, the first-class carriages have "individual seats" which means you're not sitting next to or sitting opposite anyone. The space is entirely your own and you can spread out over the little table. I specifically booked one of those seats to enable me to work.