Is there a direct bus from Hangzhou to Yunhe Rice Terrace (Chongtou Town)?

No direct bus can take you to the scenic area.
You can take long-distance bus from South Bus Station, get off at Yunhe County Bus Station first.
They depart at 10:10, 12:40 and 16:20. The ticket fare is CNY 130 per person.
After arriving, hire a private car to get to the scenic area directly.

Do you know how long does we have from the South Bus Station to Yunhe County Bus Station? And has it any (cheap) accommodation in the scenic area?

The duration is about 5 hours.
Yes, there are many local guest houses in that area. Most of them have clean living environment and warm service. You can choose one when you arriving there. Have fun!