If you only have a day then, of course, its a decent option.

However, there is probably at least 4-5 hours driving involved in a day trip like this which doesn't leave much time for seeing anything.

Windsor is a very short train ride from London and you could do that any day during your trip. Bath is about a 90 minute train ride, and I am assuming there are options for day trips to Stonehenge.

If you've got the time, do Windsor whilst you're in London and do an overnight stay in Bath by train, doing the city on the day you arrive and Stonehenge the next day.