It's not the same class of train, but part of the same family: I traveled on a class 180 between Retford and Doncaster back in February and that was making a strange noise all the way! I think it might have been something to do with the transmission (can anyone confirm this?). It was a Hull Trains service, and they have had a lot of failures lately.
With regards to the air conditioning, again it's a class 180, but a few years ago on the way down to London (again with HT), I noticed that the end of the coach my family and I were sat in was quite warm (it was a hot day, but it seemed to be blowing out warm, or at least uncooled, air), while the other side of the coach was nice and cool. Typical as we had seat reservations! Are there two separate A/C systems per coach? Does this apply only to modern units, or does it apply to older trains (HST's, 225's etc.) as well?