I've been using a 1l Nalgene bottle to carry water for at least 15 years and it still doesn't impart any taste I can detect to the contents. Of course I might have picked up BPA poisoning, but that's a different issue.
To answer my own question, the Melmerby shop is still open and in pretty good condition. Both the downstairs rooms are clean enough and have good stoves, and the upstairs rooms are quite habitable, though a bit dusty. I would have given the one we were sleeping in a sweep out, if there had been a brush available. There's a stream pretty close at hand; the water is a bit peaty, but perfectly drinkable.