Night train from Edinburgh to London?

Yes, As always, for full info consult the infamous man from seat 61: http://seat61.com/CaledonianSleepers.htm
Website of the company operating the train: https://www.sleeper.scot/

The train is mainly intended for people travelling from further north in Scotland, as a day train from Edinburgh to London only takes 4½ hours.

Why would you want a night train from Edinburgh? It is short ride. You would either have to get on in Edinburgh quite late or be in London very early.

You don't have to leave the cabins until 8:00 at Euston, although you can't get on until 23:00 in Edinburgh (although if going first class you can use the lounge).

Not much of a fan of sleepers myself, because I've not managed a decent sleep at all on the few ones I've been on. Other people might though.

The new operators of that line - Serco - have made an effort to upgrade the service.

I haven't heard of any problems with them.