We went to London for several days. I'm hoping to write more about some of this later, but meanwhile, some unorganized notes:
Food prices: whoa.
We booked a two-day pass on the "original tour", an on-again, off-again bus loop with several routes. (The main route has live guides; the rest have recordings.) This was a good way to see a lot of the main sites; you can get off at anything that seems interesting and pick up another bus later. We didn't do enough of that "getting off and back on" thing; I would do that differently in the future. (That is, we ended up chewing up time to, on our own, get back to some of those places later, when we didn't really need to.)
That bus tour comes with a riverboat tour on the Thames. That is not worth the time; there's not much to see from the river, really. I think that would have been true had it been sunny and warm, too, but I can only speculate as it rained every day we were there. (On the other hand, there is quite a bit to see from the Seine, so that river tour is quite worthwhile.)
The London Underground served our needs very well. Our hotel was within walking distance of three different stations, signage was very good, the on-train announcements were excellent (upcoming stops, where this train is going, transfer points, etc), and we never had to wait more than a few minutes for a train. I do wonder, though, how those with mobility issues can use it; I saw no lifts and there are a lot of stairs and escalators. Yet one of the stations we passed through regularly seemed proud of its track having step-free access. I never did figure that part out.
Street signs, on the other hand, were often lacking. We had to rely fairly heavily on GPS and map apps to figure out where we were and where to go once we got off a train. We would have been seriously hindered without smartphones. (Fortunately, T-Mobile's data plan works overseas without extra fees -- or so they told us, but of course we'll check the next bill.)
We bought a powered USB hub (with international power plugs as a specific feature) to charge phones and tablets and tested it for several days at home. It died a day into our trip -- shorted out, it appears. Fortunately we also took conventional adapters, but must remember to write a bad review for Amazon.
We also bought a couple of travel umbrellas (small enough to fit in a coat pocket). They were flimsy, hard to open, ugly, probably made in a sweatshop in China... and I'm very glad we had them.
We booked a day-trip to Paris. Seeing the city was nice, the tour guide was so-so, we didn't really spend enough time in some of the places, and the organizing tour company was terrible on logistics. If doing it again, I would buy our own Eurostar tickets for the train to Paris and then book a local tour separately. We booked through Viator (local operator: Evan Evans). Must remember to write a bad review, err, somewhere. (Where do people review tour packages?)
On the other hand, the day-trip we booked through Viator/Evan Evans to Oxford and environs was very well-done. Must remember to write a positive review somewhere.
Anything that could be tied to the Harry Potter movies was. This is where they filmed such-and-such scene, this room was the model for the dining hall, this chess set was the model for the giant chess pieces in the first movie, $actor slept here... Harry Potter and Napoleon were the common references, with the latter definitely taking a back seat.
When in London one goes to the British Museum, of course. While there we took the guided "highlights" tour, a brisk 90-minute run through selected exhibits all over the building. I thought that was a huge win; yes we also spent a lot more time wandering around on our own, but the place is huge and this way I got at least tiny samples of rooms we never would have gotten to otherwise.
There are two basic approaches (that I've seen) to museum exhibits: "display stuff" and "tell a story". The Tower of London tends to the latter -- so they channel you to walk through spaces along a certain path, stringing out documentation and related sidebars and stuff along the way. Both styles work, but the latter doesn't lend itself to sampling -- if you want to see part of it you walk through all of it. We did a lot of walking that day (and a lot of stair-climbing).
We saw two shows, Wicked (which was excellent!) and Spamalot (which was silly and fun). I wish we'd seen more, but it wouldn't have fit -- the day-trips took out two evenings, and we also didn't want to be up late the night before the Paris trip, which (allegedly) had a 5:45AM call at the train station. (It didn't really; that was part of the bad logistics.) But still, two good shows!
Some may recall that, a year and a half ago, Air Canada badly messed up most of my flights and in the end said "tough luck". On this trip we flew United; on the return trip our first plane was late and it looked like we were going to miss a connection (especially since we hadn't known that we'd have to change terminals at O'Hare and go through a long security line all over again), but fortunately the second plane was also late so we made it. But I'm telling this story because, while we were in that long security line, United was busy pro-actively confirming just-in-case seats for us on a later flight and sending us email about it. What a difference in customer service!