Good luck with the BCQ, I'm hoping to hit the half way mark this year, as I've been saying for the last three, it's only taken 17 years so far!
Nearly all me train travel has been with a full sized bike, I've obviously been lucky, 100's of trips and only two issues, one having to wait an hour to get on the next train and the other a taxi provided when a delay meant missing the last connection.
I do have an Airnimal, 24" wheel Joey, not the easiest fold, not hard just not instant. It's fun to ride, a little slower than my other bikes, but not by much. They come up secondhand from time to time and good condition examples fetch around £500. I've been traveling by coach with it, not as comfortable as the train, though a good bit cheaper and IMO the bike is more secure.