Ciao Jules,
So you're looking for something similar to stay at, similar to Castellina, but closer to town so you can walk to town for dinner/evening strolls? Many of the farmhouses often are in the open countryside... and unless they are practically in town, I'd still recommend to drive instead of walk as many of those main roads are narrow and dark at night, not made for pedestrians.
So I'd suggest staying in a town next time as opposed to the countryside... I'd recommend Volterra or San Gimignano or Colle Val d'Elsa. Did you visit any of these?