I've used the Caledonian Sleeper a couple of times. The first time it worked reasonably well, I got a reasonable amount of sleep. The second time not so much, not really any fault of the train, I just didn't relax enough to get a reasonable amount of sleep.

Both times I'd say well rested would be a stretch. The first time felt a bit like a magic carpet in that I got somewhere while using up no useful hours but it still wasn't perfect.

The lowland sleeper London-Glasgow/Edinburgh isn’t long enough for a good nights sleep in my view.

Yeah, you can stay on it for a bit longer after they arrive but you'd have to be very asleep not to notice the lack of movement and noise of the station around you. Funny enough the best night I had on it, it was delayed by a few hours (normally a horrible thing on the train but perfect on a slightly too short sleeper!).

That’s exactly what I mean. I never sleep much better than I would sleeping in a car.

I suppose it’s the novelty of sleeping in a moving vehicle, my flight attendant friend said it took them a while to start sleeping well on long haul flights.

Perhaps with a lot of benzodiazepines or drowsy anti-histamines I could attempt to sleep well in a sleeper train, but not normally. Happy for those who can of course.

Gotcha. It's the same for me on an airplane (I think maybe because I'm unable to fall asleep on my back), but I didn't have problems on the sleeper train.

Do you think it's the noise for you, the movement, or something else (like lack of privacy)? I started taking earplugs with me for any kind of trip now, they are a godsend.

Sleeper train can be a great experience. Unfortunately, this was not an option when I was young either due to pricing or due to availability. At least in Europe with the InterRail ticket.

Couchettes are cheaper, lower-comfort bunks.

Most sleepers also offer cabins with proper beds (for a premium).