I believe Crewe is, I'm told there are sometimes, for example, people arriving from the last Glasgow train one evening who then sleep in there waiting for the 04xx Cardiff service the next morning. I'd have to double check however as it's a long time since I was told that. Carlisle I'm not certain on but I would, at a guess, say it is open overnight.
I visited Carlisle on a Friday night last summer, once the sleepers had been through the station was locked up for the night. (Embarrassingly including me still being in it)
Last time I was at Carlisle overnight, I'd arrived around half 11ish and one of the station staff approached me, whilst standing on the South end of the platform and asked me if I was staying overnight, he was pleasant enough, when I replied yes, he just asked me to inform someone, next time I visit. Consequently I had to seek him out for the call of nature and was told to use the staff loo, near the North end of the station. I was also told, I could sit on the pendo if I wanted.
I visited Carlisle on a Friday night last summer, once the sleepers had been through the station was locked up for the night. (Embarrassingly including me still being in it)