We have done premium economy too.
I have been to Europe/UK 3 times, and it was once on coach (brrraaaaiiins....I am the living dead walking...got to hotel and collapsed. This was back in 1996 on British airways, I was in my teens and could not do anything that first day. My whole family was exhausted. No one slept. We had 3 screaming babies the whole trip, and one couple was arguing because their baby was crying...) we all fell asleep in the room and barely made it for dinner. First day totally wasted. Second day, I was still a bit out of it, but got better as the day went on.
Second on British airways premium economy, which is a separate section...first class seats, coach service. No lay flat seats, just roomier. (Little less walking dead, we did a hop on hop off bus tour and napped and loafed on the first day.) I had a hard first day, but better then coach. I think there was a baby crying in coach, but we were in a separate cabin so the sound was muffled.
Last trip, business class. I slept soundedly, woke up a bit, but got back to sleep. We got noise cancelling headphones from the strewardess, and even if my hubby was snoring, I heard nothing....I wore them to sleep! I was wide awake when we touched down in Barcelona. I tired easily though...but we did a walking tour that night and toured the afternoon. I slept soundly that first night and woke the next day for the start of our cruise in fine shape.