Thanks for the feedback. I was missing the "Fixed Links" data, which covers any transfers that aren't part of the normal rail network (e.g. walking/bus/tube). I've just added that, so the tube routes via London should work for you now.

The routeing data is pretty complex - there are layers on layers of data files and rules to cover all the edge cases and weird stations/routes. It's been really fun to dig into it.

I'll look into adding more possible connections to see if it can find the Penzance route - I'd be curious to know if anyone has ever actually completed the 27 hour journey!