If we were to look in at West Bay around lunchtime, then quite a good way home would be north out of Bridport on the A3066, picking up the A30 just east of Crewkwerne. Then, Shaftesbury, Salisbury, Stockbridge, at the A303 petrol then depending on the time , either A30 to Camberley, south on A331 to A31, A3, M25 home, or if time's short M3 to Junct 4 from the A303 petrol stop to pick up the A331/A31/A3/M25 etc. Just a thought, I use this route when I do a Cornwall and back in a day trip.