Is there a direct bus from Tunxi to Wuzhen? Which station to get on and what are the times?

I'm afraid not. You can take a bus at Tunxi Bus Station to Hangzhou first. You will be taken to Hangzhou West Bus Station. Then you should transfer to Passenger Transportation Center to take a bus to WZ.

Buses from Hangzhou to WZ are scheduled from 07:00 to 18:15 and the whole journey takes 1-1.5h. And from Tunxi to Hangzhou, the bus duration is around 2.5h.