Looks like you'll be near Hampstead Heath, great view of the city on that hill, I lived and worked at Pax Lodge, the youth hostel/world centre that the Girl Guides/Girl Scouts runs (right next to Air Studios). The pub on Rosslyn Hill named The George (one of many in the city) was really good. I found the Euston Flier Pub, across the street from the British Library (a must-visit) was excellent too. Honestly, I think the list of bad pubs would be way shorter than good pubs :) I don't know that I've ever been in one that I would have called "bad". :) They have had different styles, but been good all over. The one near Windsor Castle was great too.
Hm, stuff not in the guidebooks...., Globe Theatre was good, but my daughter dressed up, and it's an outdoor theatre, so in the evening it got cold (they gave us blankets, but I think we got lucky). Strongly prefer buses over Tube for 2 reasons, one is that I'd rather SEE the city instead of seeing a dark tunnel :) and because I have slight double vision and the Tube's escallators are super steep and super fast, so I love buses.
Anything you have a membership in here, that also might have members there, is worth looking in to. I belong to Mensa here, so I found out how to get access to the British Mensa calendar, and poof, I had local friends at a pub there super easy. Meet-up.com is also very active over there, so there could be special interests that would connect you to people there. I find there are different online calendars for things like dog shows and specialized things, & they are worth the time to track down. Even if I don't know if I could get to it, it's nice to have a few things listed on a paper that can turn into a spontaneous get together. Astronomy clubs can be great, a bunch of things are possible, there's evening presentations at Pax Lodge for scouting people, just a load of options when you look. The Chelsea Football club also has a ladies team, so it might be easier getting tickets for those kind of things.
Camden Market's OK, mostly the same stuff in many of the stalls, lots of flags on things :) but can be entertaining with the street performers on weekends and there is some variety of fashion and fun things. The Pax Lodge volunteers would go there to get the very popular scarves and things like jewelry.
I've gone 3 times, with my daughter twice, once for that 2 month stay to live and work there, and then another week to celebrate her Bachelors degree. I found that sometimes, when you have phones that definitely work there (can be a challenge), it's nice for travel partners to be able to go do their own thing for half a day. If there's disagreement on where to go, it's OK to do different things and then have lots to talk about at dinner that night :) My Google Fi phone promises that it'll work there, and at the same price as here. I'll report back on it after my next trip.
Windsor's excellent, and if you get your ticket validated, you can get back in for free another day. I did overhear that someone who wanted to get in later in the day, like after 3PM or 4PM, could not do it because they bought their ticket through some other service or web site, and not through their box office. They started to have a changing of the guard too. Found GOOD prices at shops and restaurants there too. Low stress, small town, and lots of history.
Would not recommend rides in those big tricycles with the carriage-looking seats in the back, the one we took hit at least one car from not stopping early enough. But maybe the rest of them are safe.
The best thing that we did was when something was really magical, we stopped and really took it in. Just watching the lights come up all over the city, including watching Big Ben light up, (may not be an option any time soon), from a bench on the Thames, was way better than a lot of high priced attractions. Find what's meaningful to you, and you'll have a great time!