I will be traveling to London this July and am seeking advice on where to stay for a couple of nights outside of London. I would arrive on a Sunday (from Dublin) and would like to see Oxford, Highclere Castle and Avebury on Monday and Tuesday. I would prefer to stay in Highclere or Avebury to have a more rural feel and would think that two nights in either is better than one night in each place. I will have three full days in London afterwards to spend time with friends in the capital till my flight home the following Saturday so most likely will head to London on Tuesday afternoon/evening.
I am not planning on renting a car although I could if it's really worth it. I'm usually the navigator but since I'm traveling solo I won't have somebody to drive or navigate for me (which is better than just using a GPS in my opinion). From what I've read Oxford is easy to get to by train, Highclere can be reached by train/taxi (via Newbury) and Avebury is reachable by car.
Are these three places easily visited without a car in two days or might it be too much? I could cut out Avebury if needed but was hoping to get a different experience there as compared to Stonehenge which I visited the last time I was in England. I've thought about day trips but staying in Bath last trip whet my appetite for overnight stays outside of London.
Any advice would be appreciated!