If this is a one off then I think your being a bit petty. Aside from the fact that the course might have enhanced your knowledge, ability, worth, prospects having an argument after the event about an hours travelling time doesn’t seem a good thing to do.
Particularly as very few people get paid travelling time and most do it every day. There are folks in the valleys and elsewhere who spend more than two hours every day getting to and from work in Cardiff.
If your asked to attend another course ask the question up front.
I’m guessing that you have a long working career ahead of you.