Recommendations / favorites in London after seeing the main sites?

Have you looked for temporary exhibits? For example, the National Archives has a MI5 exhibit

Have you already visited the Courtauld Gallery? It's wonderful.

Well, definitely see the Treasure Room in the British Library.

Bletchley is definitely worth the effort. I thought I’d spend 2 hours there. Spent 4. Very well done!

Have you seen the Crystal Palace Dinosaurs?

Toured Wimbledon?

The Hunterian Museum is interesting and afterwards be sure to visit the Seven Star pub. 5 minute walk.
Cozy pub, fab pub cat and tasty pasta dishes.

Walking along the Thames River Path is enjoyable. So is strolling along the Regents Canal Path. Watching the narrow boats, dog walkers…

If you want to get out of London proper there’s the Parkland Trail. I enjoyed a meander on it from Finsbury Park to Crouch End.

Enjoying the massive Richmond Park and seeing the fallow deer is a great excursion if weather is good. Then buy cheese at Teddington Cheese if you exit the park by where the Royal Star and Garter Home is located. If timing is right u could have a pint at the Victorian Inn ( no food there) and or go into the pleasant Books on The Rise. 15 -20 minute walk to Richmond Station to board an Underground train or SW train back to Covent Garden. Allot 60 minutes.

Definitely search out street markets. Brick Lane, Columbia Road Flower Market, Broadway Market in Hackney, and Maltby Market.

Must say check out Spitalfields. Depending when in the Fall you are traveling ( I go in November ) you can find Xmas ornaments, stocking stuffers and boxes of Xmas cards.

If LP lovers or if you know an afficiado and your dates coincide; https://oldspitalfieldsmarket.com/events/vinyl-market

Been going to London since Nixon was President. Never fails to provide new sites to explore and enjoy.

Enjoy.

I don't know your interests or what you've seen.

Richmond, Kew Gardens, Ham House, Strawberry Hill House, Hampton Court Palace.

Lots of good suggestions- let me add Sir John Soane's Museum - Sir John Soane's Museum (an amazing collection in a single home) and Spencer House.

We loved spending time in London’s parks. St. James, The Regent’s Park (my fave), Hyde Park. If the weather is nice, pick one or two to spend some time in. There are paddle boats in Hyde Park on the Serpentine.

https://www.royalparks.org.uk/visit/parks/hyde-park/boating-serpentine

Hampstead Village (and Hampstead Heath) is a short bus ride from London. Two really cool places that make you feel like London is a million miles away. Parliament Hill (in Hampstead Heath) is a lovely place to have a picnic and see the London skyline.

Speaking of picnic possibilities, if you’ve watched the series One Day on Netflix, you may have seen Primrose Hill. It offers a spectacular view of London on a nice day. It’s also in The Regent’s Park.

So many possibilities! Have fun together!

Like the poster above, I enjoyed Hampstead and the Heath in March. I decided to make a day of it on a Sunday. I took the tube to Hampstead and joined the London Walks' Hampstead Village and Heath Walk, booked a 1:30 table for Sunday roast at The Spaniards, then walked over to Kenwood House to view the art collection. Afterwards I walked back to the Village through the Heath and stopped in at The Holly Bush for a cool drink before heading back to central London. A lovely day. Felt like I was in the country, but never left London.

Another afternoon spent walking along the South Bank of the Thames from Westminster Bridge to Tower Bridge. Lots to see along the way and a few stops at historic pubs with views. Only the overcrowded Borough Market was disappointing.

How old is your daughter? Interests?

The V&A has a Young V&A and V&A East if you have never been. The Kensington location has a couple of temporary exhibitions - Cartier and Marie Antoinette Style - which may be of interest.

Design Museum.

I also enjoyed the Photograghers' Gallery very much.

If you are interested in walking and history, you may be interesting in "collecting" blue plaques.

Have a fabulous trip!

Thank you all so much! Wonderful suggestions. I love the idea of making good weather and bad weather lists, and you've given me so many good ideas for both. Very few things on here we've done and most I haven't heard of! My daughter is 19 and our trip is probably end of October, so weather may or may not be good for parks but I love the idea of a picnic in the park with a view of London's skyline, and am excited to check out many of these museums we haven't been to. What a wonderful resource this community is!

The Courtauld Gallery is definitely now on the list, I don't know how we've not put it on the list before. It is going to be hard to pick among the house choices, although based on just a quick look, Spencer House might be it!

I'm too squeamish for the Hunterian museum, I think. Spitalfields was on the list although don't collect LPs. My daughter is in charge of finding new food markets as we don't need to repeat Borough Market!

Do you recommend a good source for temporary exhibitions? I always forget to check for that. We will unfortunately miss the MI5 exhibit, I would have enjoyed seeing that.

Thank you all again!

Have you been to the Wallace Collection?

I don't see Greenwich and the Royal Observatory there being mentioned yet. We enjoyed it immensely, and it's easy to get to.

Denisek, having the good and bad weather options is a great idea. We went the first into the second week of October last fall and had some really nice days: sunny, just a long sleeve shirt, light jacket, to cloudy/rainy ones where we needed a sweater, scarf and gloves. What makes London such a great place to visit us the potential for doing so many different things! Enjoy your trip!

If you and your daughter are in relatively good shape, the London Monument is a nice quick attraction. Built to commemorate the Great Fire, you can climb up the 300+ stairs to get a view of London. Plus you get a paper award showing you climbed up the stairs and survived. :)

https://www.themonument.org.uk

We love history and walking tours

If your trip is in October, you may still be able to visit the free, outdoor Saving St Paul's exhibition outside the Cathedral.

www.stpauls.co.uk/whats-on/exhibition-saving-st-pauls-watch-and-second-world-war

Courtesy of the forum, I'm pairing that with London Walks The Blitz, on Thursdays.

https://www.walks.com/our-walks/the-blitz-london-turned-crimson/

We went to both the British Library and the Museum of the Home on our recent trip. We loved both. The Museum of the Home was really well done, had a great garden in the back, and was a nice break from all of the crowds at other sites. We were a little disappointed with the treasures room at the British Library as it seems like they're in the middle of some maintenance work so many of the exhibits were empty. But we loved the audio exhibit in the lower floor where you can listed to all sorts of stories about British life, linguistics examples of accents, books read by famous authors, etc.

Two places that just missed the cut for us were the Foundling Museum and Novelty Automation, both will be near the top for our next visit.

The Old Bailey. London’s criminal court. We spent two hours there watching British Barristers ply their trade. Spellbinding. Even better than Witness for the Prosecution.. And you have a window into another side of British life.

Staff suggested the most interesting trials to attend.

You can bring no backpack, no large purse, no cell phone and no camera. For info see https://www.cityoflondon.gov.uk/about-us/law-historic-governance/central-criminal-court

(Edited to add - We were in the public galleries, rather than on a tour that the website also mentions)

Others have mentioned Sir John Soane’s House, the Wallace Collection and the V&A, all of which we enjoyed very much.