Easily the most comfortable place to stay is this chic resort run by Lhasa's Shambhala Serai group. It has its own riverside hot springs, 5km before Tidrum, and the best split-level suites boast their own private hot-water tubs. Simple food is available, but don't expect much in the way of spa service, only towels and flip-flops (thongs) are provided.
If you have trouble getting in touch with the resort directly, try booking through the House of Shambhala in Lhasa.