For people who travel frequently, a lot of the travel experience can be optimized.

• I haven't tried this but I know others who prefer sitting in the first class coach on trains. It can cost as little as £10 extra for Paddington-Oxford, and it helps them get enough elbow/laptop space to be productive.
• Paying for wifi on flights is such an awesome deal. I can be productive for many hours for just $15-40 depending on the airline and flight duration.
• Optimizing the airport experience is pretty straightforward. In the US, TSA Precheck and Global Entry cost ~$25/year and save you at least 10 minutes (and often an hour or more at peak times) per trip at security and immigration, respectively.
• I also try to book flights on the same airline alliance where practical, which helps me accrue status and use business/first class lines and lounges everywhere. I estimate I save at least an hour per trip through a busy airport as a result, since I can arrive at the airport later, go from check-in to lounge/gate in 5 mins instead of 45, not wait for my boarding group, etc..
• Depending on how much you value your time, it might be worth it to switch cabins on flights. Moving from economy to premium economy / business at check-in often costs £100/£600, respectively, for a 10+ hour flight. I know people who value their time at >£150 per hour, and the productivity gains from sleeping well on their flight would make this tradeoff worth it. You can also use credit card points for this.
• I've tried traveling using running shoes vs other footwear. I estimate I walk at least 20% faster with running shoes on than with boots or walking shoes, based on the number of people I pass up and based on how much I beat Google Maps walking time estimates by.