If you can purchase a detailed Ordnance Survey map of the Cotswold region then you could follow this route that I think you'd like.
From Blenheim Palace the main exit for cars will take you south and out into Bladon. Turn right when you exit Blenheim park and head to Bladon village and St Martin's church. There you will find the graves of Sir Winston and Lady Churchill and other family members. Continue to Witney but when you get to the first crossroads in the town follow signs for Minster Lovell. You will soon be on narrow roads following the Windrush valley. This is where close examination of the map is needed as lanes peel off everywhere here to little hamlets of stone cottages. The village of Minster Lovell is one of the most beautiful villages to see (London Walks take people there on their Explorer Days) and just down a side track that says 'Unsuitable for Motors' is St Kenelm's church and the ruins of the 15th century Minster Lovell Hall.
Continue through the village and follow the valley road to Asthall where there is a pub called the Maytime that serves great food. Continue via Widford or Swinbrook (villages on either side of the valley) and end up in Burford. Plenty to see and do here. Shopping, town museum, St John's Church.
Not to miss: Bibury one of the loveliest villages in England; Bourton on the Water, another lovely village( both are heavily touristed so best seen either early in the morning or later in the evening, say after 6pm)
Hidcote garden, see the following website for more.
BUrford is also lovely, though not a chocolate box village as the other tow.
Broad Campden has some fabulous thatched houses.
Fairford church has some of the most ancient stained glass in the UK.
It'll be a fairly straightfoward route from Burford to Bath. Leave the A40 and head down through Aldsworth where the Cotswold breed of sheep were last commercially farmed, to Bibury and stop there to visit the famous weaver's cottages known as Arlington Row. Then through Barnsley to Cirencester. Bit ugly in parts here, especially the edges of the town but if you can get into the centre there is a magnificent church and market place. If you take the ring road you'll see very little of interest save for the earthworks of the Roman Amphitheatre dating from when this town was known as Corrinium nearly 2,000 years ago. You can then take the famous Roman road, the Fosse Way, straight to Bath, past the source of the Thames near Kemble, through Tetbury and past Prince Charles's place at Highgrove and the Badminton Estate then finally over the M4 and down into Bath itself.
We bought an ordinance map and asked the locals their favorite villages, then marked up the map with a marker. Favorite villages - Upper and Lower Slaughter, Snowshill, Stanton, Bibury. Bourton-on-the-Water and Stowe-on-the-Wold are nice larger towns. Blenheim is the nicest palace I've been to and I really enjoyed Warwick Castle. Sure it's touristy, but I enjoyed seeing the castle all the way from the Norman Invasion through the Victorian era. The costume museum in Bath is worth a look.My favorite attraction in Stratford-upon-Avon was Anne Hathaway's house.
We liked it so much, we're headed back next summer - renting a cottage in the Cotswalds for a week!
thank you all