For creating a realistic route with current speeds per track section, signals, switches, etc., there is an online map where you can find this information for the entire world: https://openrailwaymap.app/#view=1.91/20.53/0 It might be possible to create a connection (similar to Google Maps)!
While Open Railway Map is nice to get a general idea, there are mistakes if you dig deep enough so you should always verify it with cabviews. Look at all the signs and signals along the route to to get the real data.
Also make sure to use sectional diagrams from network rail. https://www.networkrail.co.uk/indus...rs/national-electronic-sectional-appendix/#SA
