Finally organized an itinerary for September

I guess you have reasons for flying to and from Paris on this trip to England, hope it's not just for a café lunch. ;-) But better make it brunch, since you have to be at the Eurostar platform at least half an hour before your 12:43 departure. Many recommend sooner. That's after an airport-type security check, so allow plenty of time. Most likely your café will be near Gare du Nord.

For Sunday I'd suggest visiting the Tower first, since you'll get off the boat there. Take a Yeoman Warder tour if you can and leave time to explore on your own. Skipping the Crown Jewels, if you can bear it, will save much time. Then St. Paul's is an easy walk through the City, which will be quiet, and you should have time to go in and maybe climb up the dome if you want.

Others know them better, but my understanding is that the Oyster Card is the way to go -- it automatically gives you the lowest available fares for the tube and bus trips you take each day. Have a wonderful trip!

Hi, sounds great but you may need longer at the Churchill War Rooms as the Museum in there is very comprehensive. It is an absolutely fascinating place. Oyster cards are the way to go for transport. Easy to buy and use with top up via machines or ticket offices at the Tube Stations.
Probably too much crammed in on your Hyde Park Day. If its lovely weather you could wander through the Park and then have delicious Belgian Waffles at the Choc Cafe in Harrods. Very nice and fabulous service.
Good to see you are visiting Avebury. Wonderful atmosphere and you can touch and wander among the stones. The cafe there has clotted cream with their scones. Delish! The Cotswold area is lovely to drive through. Lots of quaint villages and pubs to eat at.
Make sure you leave enough time to get through the security to catch the Eurostar from St Pancras as it can get very busy. Luggage goes through xray machine and they pat you down as well.
If you had more time a visit to Hampton Court Palace for the day would be marvellous. Hope this helps, cheers Virginia

Yes since you spend effectively zero time in Paris, why take the Eurostar? Take a connecting flight instead - should avoid some immigration queues at least. You would be in your hotel in London before you leave Paris on your schedule.

If you flew from Paris to London on your day of arrival you'd avoid a lot of transfers and expense going into Paris after a long overnight flight. Right now flights cost about the same as a Eurostar fare.

If you wanted to spend a few hours in Paris you could fly from London to Paris in the evening before your return flight, spend the night near the Halles/RER station giving you a morning to enjoy Paris before your train to CDG and your flight home. Or you could just fly into CDG on the morning of your flight and continue on, leaving Paris for another trip.

I should add that we took the Eurostar from Paris to London last month and I would recommend being in the check-in line for security checks and 2 passport controls about 1 hour prior to your train departure if you do decide to take the Eurostar. There were very long lines when we were there and some frantically late people.

You really should find a flight from CDG to London. You will save yourself SO much time coming into town, etc etc. Even if the air ticket is more expensive, it may not really be so much more when you consider the value of your time on vacation. You will lose hours and hours of time by coming in and taking the (still expensive) train rather than simply finding a flight from CDG to London and back.

Also I agree that you don't leave yourself nearly enough time at the Churchill War Rooms -- only 1/2 an hour or so by the time you need to leave and position yourself for the Horse Guards.

Sounds like you have done lots of good planning. I would suggest the parking in Oxford is crowded and the town is NOT car friendly. Perhaps you might take the train to Oxford, go to the rental lot and 'get' your car BUT leave your car and luggage parked in the car rental lot, tour Oxford and then drive to Chipping Camden when you are ready to leave Oxford. Avis has one very close to the train. It would certainly make your first day driving easier since you skip the whole getting out of London traffic snarls.

Trains from London leave Paddington every half hour, costing around £20 for a single trip, and takes approximately one hour. For national rail inquiries, call 08457 48 49 50 or visit their website. Note: cheap tickets can be purchased in advance for as little as £10 return. Check the website of contact National Rail for details.

Mona, Kim and Kate have very good ideas above, imho. Flying between Paris and London will save time and tire you less. Flying to Paris Friday night will give half of Saturday there. You could sleep in a CDG hotel, check out but leave your bags Saturday morning, pick them up on the way to your homebound flight early that afternoon. Also training to Oxford to get the car is a good idea, I think you can return it at Heathrow without a dropoff charge. If you switch some days around, doing your Friday London sightseeing on Tuesday and moving your Tuesday-Thursday road trip to Wednesday-Friday, you could fly back to Paris when you drop off the car. Also I agree your time at the Churchill War Rooms may be too short. But 9:30 is opening time, so you'll have to evaluate the tradeoff with Horse Guards. Fortunately you can do that on the spot.

I really appreciate your comments and ideas. To explain the Paris thing:

-- We found insanely cheap business-class tickets JFK-CDG, which is why we are going to Paris in the first place.
-- When we bought the plane tickets we planned to spend a day and a night in Paris before going on to London, but then we found out our daughter-in-law (she and our son live in London, thus this trip...) has to go to Mexico for her brother's wedding the morning after we arrive. (That was an unexpected change. Wedding was supposed to be in August.) And she will return the night before we have to leave. So if we want any time with her, we can't spend time in Paris on this trip.
-- Our son recommended Eurostar because the St. Pancras station is just a few blocks from our hotel and his flat. We bought round-trip premier tickets before really researching the CDG to train station piece. So, we are going to just deal with the situation, do a lot of people-watching while we stand in long lines, etc. It will be fine. We are packing very light so we can get around easily.

Churchill War Rooms schedule is very flexible. If we want to stay there longer, we will just miss the Horse Guard thing. I deliberately planned it that way.

Love the idea of renting a car in Oxford. Will definitely look into that.

For the Friday schedule, in what order should we attempt that list? We'll start at the top of the list and go until we run out of time or energy. What could we miss without regrets?

B&B has been booked for Tuesday/Wednesday nights for several months. No changing that plan!!

Keep the ideas flowing. THANK YOU! And if anyone wants ideas/suggestions for my part of the world, let me know!

Thanks for the explanations -- not that you owe any! :-) For a cheap transatlantic business-class flight I'd do a lot of zigging and zagging on the ground! And your family's availability obviously drives much of your trip.

Your Friday seems quite doable to me, basically a northwest progression across Hyde Park, you could walk it all with a stop for lunch or tea at the Orangery near Kensington Palace. You'll pass near the Albert Memorial and the Princess Di Memorial. Might have time to visit the Victoria & Albert Museum, slightly out of your way, if the decorative arts interest you. Of course if you'll be buying a lot of stuff at Harrod's you might not want to spend the rest of the day on foot. From Notting Hill Gate the Circle Line will take you back to Euston Square or King's Cross/St. Pancras, whichever is nearer your hotel.