Whether or not its a bad idea, its probably better than not going. Unless you can find another option then go for it.
I had an interview with BDO. They offered £50 travel expenses and no accommodation expenses - the train would have cost over £100 so I booked a really early coach. The night before they changed the start time and made it an hour earlier. My coach was delayed and I ended up being really late. What I should have done was called and ask to be put on to a different AC but I didnt and showed up almost half way though, very flustered.
It was obvious that I wasnt going to get an offer...even if I had done well in what I did, I missed enough to count myself out. One of the comments from the partner interview was "I'm surprised you didnt just book a hotel". Perhaps some people can afford to do that, but I certainly couldnt afford £150+ per interview when that was the second time I'd had to make the journey.