Follow the A4 for Bristol, at the end of the dual carriageway take the 2nd exit (A39 for Wells) from the roundabout (by the Globe Inn).
Drive through Corston and on to Marksbury. Directly after the Church in Marksbury turn left and follow the brown Heritage signs for Priston Mill (2 Miles from A39). 

(for best route using sat nav enter via Marksbury BA2 9EQ)

From Bristol follow signs to Bath, which will take you on the A4.
(From M4 Junction 19 onto M32: Exit on Junction 1, Follow A4174 Ring Road for Bath, and join A4 towards Bath)
Drive along the Keynsham bypass, through the village of Saltford (keep to the speed limit - watch out for a camera coming down the hill) and take 3rd exit (A39 for Wells) from the roundabout (by the Globe Inn).
Go through Corston and on to Marksbury. Directly after the Church in Marksbury turn left and follow the brown Heritage signs for Priston Mill (2 Miles from A39).

(for best route using sat nav enter via Marksbury BA2 9EQ)

Click on the map for larger view.