A day trip of Salisbury Cathedral-Stonehenge-Bath: Three-Part Question

Staying in London for a week - Airbnb not far from Paddington. Thinking about a non-London day trip for one of the days. Based upon the interests of my crew, Stonehenge/Bath and Oxford seem like good choices.

Part I: Is a day trip to Salisbury Cathedral (AM) - Stonehenge - Bath (PM) possible or too much? I know you can make a day of Bath, but can you hit the highlights in an effective manner? I have heard compliments of Salisbury & Salisbury Cathedral (plus they have an original copy of the Magna Carta). Making a loop of it if you will.

Part II: does this require a rental car or can public transportation do the trick?

Part III: the Oxford tube the recommended travel solution for Oxford?