Best London Day Trip to Picturesque Village

One possibility is Canterbury, though I wouldn't call it a village. It's as little as an hour from London. It has a wonderful cathedral (with stained-glass museum upstairs) and a very picturesque historic center. The tourist office runs walking tours. It is popular, so there will be lots of other tourists about. I'm sure our British and more experienced posters can suggest some more off-the-beaten-path options.

You said you're considering Windsor. I love Windsor and think that's a good idea.

But to see some countryside and small villages, look at this trip to the Cotswolds with the London Walks company:http://walks.webvanta.com/our-walks/the-cotswolds-in-spring-1-1

Windsor is great, but it’s not a village. If you want to show your relatives a village I would recommend go to the Cotswolds. You could take a train from Paddington Station to Moreton-in-Marsh, there is a train at 8:21 arriving at 9:59am. There are several trains you could take back there is a 5:38pm, 6:12pm, 7:27pm and there are later ones, it’s an hour and 40 minute trip. Once you get there you could take a cab to either Broadway, Bourton-on-the-Water, Chipping Campden, Stow-on-the-Wold or other villages. There are buses to the villages that I mentioned, but you said you didn’t want to wait on busses. If you take cabs and share the fare then it wouldn’t be that expensive.

Rye is a good choice too, and fairly close to London.

An advertorial website https://sussexbloggers.com/tips-for-visiting-rye-east-sussex/ keeps the addie bit quite quiet, and the photos are good and representative.

I like Rye and I think it meets all your criteria.

A quote from that website gives the train arrangements:

High-speed trains run from London to Ashford International with a
journey time of 38 minutes. A further train to Rye takes 21 minutes
which makes this pretty, historic town the perfect option for a day
out from the city or a for a weekend break.

Parking is known for being incredibly tricky in Rye, however, Station
car park in the town centre is reasonably priced at £2.60 per day.
This expires at 5am so two days parking will need to be purchased.

Thank you for all of your suggestions! I had considered the Cotswolds but was stuck in the idea that we would need to hire a car, as we've done in the past. Since the villages you mention are only 7 miles or so from Moreton-in-Marsh, the cab option makes this very do-able. One question: Are cabs usually waiting at the train station? I also had looked briefly at Rye, after seeing it named as one of the most beautiful villages in England, but hadn't seen the information for fast trains, which really would cut the travel time. So I'm weighing both ideas (and definitely will file the other suggestions mentioned in this forum for a future trip...)

"I also had looked briefly at Rye, after seeing it named as one of the most beautiful villages in England,"

It's actually a town rather than a village.

A good way to go to the Cotswolds is also to:
Take the train from London to Moreton-In-Marsh.
Connect with Go Cotswolds company for a tour of the villages on a small mini bus (Mercedes van).
https://www.gocotswolds.co.uk/
https://www.gocotswolds.co.uk/product/cotswolds-day-tour/
Pick up locations:

Leamington Spa rail station
Stratford-upon-Avon rail station and hotels
Moreton-in-Marsh rail station
Chipping Campden bus stop (outside the library)

Tours operate every Wednesday, Thursday, Friday and Sunday and visit a variety of towns and villages that characterize the beauty of the Cotswolds.
Do tell them from which location you want to be picked up, when you make your reservation.

We went on this tour two years ago and loved it. We were staying in Stratford-Upon-Avon (also a fun town to visit) and were picked up at the front door of our hotel. Here is a trip report of that tour:
https://community.ricksteves.com/travel-forum/day-tours/go-cotswolds-tour-with-tom-the-most-fun-we-had-while-in-england

Consider Rochester. It has an old abbey. Was founded by the Romans for the bridge. A Norman castle and a connection to Charles Dickens. I quick hour train from London.

I was very happy with my GoCotswolds tour, but I don't know how viable it is to start the day in London and meet that tour. I had a hotel room in Oxford for several nights, which put me just a short train ride from Moreton-in-Marsh.

Yes, there are cabs at the station, if there isn’t there are phone numbers listed to call and one is there within a few minutes.

I also had looked briefly at Rye, after seeing it named as one of the most beautiful villages in England

You may be interested in Brockenhurst in the New Forest as that has been voted the most beautiful village to live in in England

http://brockenhurst-newforest.org.uk/

https://www.thenewforest.co.uk/explore/towns-and-villages/brockenhurst

The train from Waterloo to Brockenhurst takes around 1hr 50 mins with no changes. There are taxi's available at the station and you can pre-book one from here: www.brockenhurst-station-minicabs.com/

The New Forest is a spectacular part of the country and well worth a visit, even better if you can make it a longer one.

I linked this incredible tour on another similar question: https://www.cotswoldtourismtours.co.uk.

It runs every day, picks you up at and returns you back to the Moreton-in-Marsh train station and takes you many places that are not accessible by public transportation.

It is coordinated with the train schedule and most of the people on it when I went had come from and were going back to London.

Explore the website thoroughly to compare with your other options.