Very nice! I've also used the Rail Data Marketplace (terrible name) to build an app that uses the live departure board data (https://apps.apple.com/gb/app/traintrack-uk/id6504205950), and it's great the data is freely available.
Whilst HN is on the case, does anyone know of an API (inside Rail Data Marketplace or elsewhere) that acts as a journey planner for UK national rail, i.e. you can input source + destination stations and it will output journey options?
It looks like TFL's journey planner API has the ability to do some of these national rail trips, only tested a few though