I rarely recommend websites but will make an exception here as it’s taught me something!
trainsplit.com is a UK rail ticket purchasing service which checks to see if your journey could be cheaper if you were to ‘stop’ at a station along the route to your destination.
For example, I often travel from Brighton to Farringdon for £39.80 standard return fare which happens to stop at Gatwick Airport during its journey. Using TrainSplit, I pay the standard return fare from Brighton to Gatwick (£11.60), then from Gatwick to Farringdon (£19.50). Total £31.10, saving £8.70. TrainSplit then takes 10% of the saving (87p) as their fee.
The rule is that the train has to stop at Gatwick; however, I don’t have to get off it (in either direction).
Pleasantly, my clients pay all my travel expenses, but it’s nice to show that you’re thinking of their bottom line too.