I know the 07:17 from Bristol Temple Meads to Swansea always used to be announced with “first class is at the rear of the train as it arrives at the station. This will be the front of the train as it departs”.
I now get to Temple Meads after it’s pulled in so I don’t know if it’s still announced like that now that it’s been replaced by an IET.
On a semi related note, that train stops at Filton Abbey Wood which has a short platform so only the front 5 car set is available there. Usually the TM announces which coaches you need to be in but this morning there was nothing besides one line on the PIS saying you need the front coaches. I could imagine that one catching out a few unsavvy passengers as if you get in the wrong half you’re royally buggered!