As I read it, you didn't do part a of the article as you didn't take a flight back to your point of origin therefore that doesn't apply, I would suggest asking BA for the cost of the hotel and the train ticket but not refund for the ticket or the refund for the segment not taken but not the onward journey. Equally BA, may say that since you made your own arrangements without authorisation from the airline, then they are not liable; in which oI would use your travel insurance.

The compensation isn't meant to be a way to profit from the airline when they weren't to blame.