I'm with with Godspeed and Mitlov. I recently sat in the back of the 3-series coupe. I am 5 foot 3 and a half.
I doubt the 1-series coupe backseats could comfortably transport people who are tall or larger than average.
I also had a hard time trying to get out of the back seat. Really inconvenient IMO, but I guess that's on par with most coupes. A car for really only 2 people. On the other hand, I was pleasantly surprised with the room and access to the back seat of the sedan. I guess I was expecting those things to be smaller. They felt better than in my TSX. But helas, I don't like the styling of the sedan rear.