We did Bath in late November a couple of years ago. Very easy day trip from London. Lots to see. Christmas market hadn't started.
Did Salisbury last year in December. Also super easy day trip. Cathedral is impressive, but there isn't much else. Christmas market was disappointing.
We've been to York several times, including as a day trip from London many years ago, As others have said, York deserves several days, but it is doable as a day trip.
Oxford or Cambridge are good candidates, too.
Be mindful of winter hours, though. Days are very short, and some attractions will be closed, or have limited hours.