Please critique my London itinerary

You will have a wonderful time!

Are you familiar with the 2-for-one offers you can get for many London attractions with a 7-day paper Travelcard instead of an Oyster card?

https://www.daysoutguide.co.uk/2for1-london

They include the Tower of London, London Eye, London Zoo, Kew Gardens (lovely in June), maybe the Sea Life Aquarium, and others. Including special exhibits at many museums. Well worth looking into.

For your hotel location, the Lancaster Gate tube station is close, but will require a transfer from the Piccadilly Line to Central Line, then backtracking. You might consider getting advance tix on the Heathrow Express (12.10 GBP if purchased 90+ days in advance) and going to Paddington in 15 minutes. Comfortable and convenient. You can walk to Number 63 from Paddington (we would).

Number 63 is in a great place to cross the street and get into Hyde Park. Keep your eyes and ears open and you might find parrots.

Good cup of coffee available in the Park, too.

Check carefully your travel to the Harry Potter studio tour. Did you mean to say train instead of tube, or do you really mean to take the Metropolitan Line tube the long ride to Watford and then walk over to Watford Junction train station to get the bus to the studio? I'd have suggested the fast train from Euston Station either non-stop or up to 3 stops to Watford Junction, walk out of the station diagonally across the forecourt to bus stop number 4 for the Knight Bus.

It sounds to me that you have a fun trip in prospect.

Do consider Lola's suggestion of the 2 for 1 scheme.

Day 4- Tower of London and area, other nearby sites.

Consider visiting http://boroughmarket.org.uk/ and https://skygarden.london/

I don't have any objection to doing a Jack the Ripper walk, but kindly do not have anything to do with the "Jack the Ripper Museum". The owner is an unspeakable bastard who got planning permission from the local council by claiming that he would open a "museum of women's history" and then opened a crappy boardwalk attraction all about women being murdered.

The OP is visiting the Tower on Sunday if my calculations are correct, and Borough Market is closed then. I would definitely recommend it, but don't visit it on the Saturday either, it's unbearably crowded on Saturdays now.

You do know that 0515 is too late to leave London if you want to see the sun actually rise at Stonehenge in June?

I love that you have left some free time and general “London Sites” time so you can work in places of interest as you discover the, or continue your research.

If you like gardens, look into wandering Kew Gardens. I bet it is magnificent in June! If your budget allows, see a play. London theatre is fantastic!

Day 2: The Tube does not go to the Harry Potter Studios. You'll need to book tickets on the coach bus from Victoria Station out to the studios tour, it can be bought with the tickets, in advance, they get booked up. When we went in 2015, My then-25 yr old daughter missed out on getting to the HP studios because she under-estimated the difficulty of getting there in any other way (and she's an experienced traveller to England too). Easiest way is to get over to Victoria Station.

Day 7: Windsor is easiest to get to from Victoria Station, there's a green coach bus that goes straight there and drops you right at the top of the hill, not far from the entrance.
http://www.greenline702.co.uk/
http://www.greenline702.co.uk/greenlineleafletjul18-web.pdf

Super comfy, lower stress. :)

To take a train to Windsor, it needs to be from ** Paddington station, that's the one that connects to the train station in Windsor near the castle. That comes in a little plaza area with restaurants and shops, you walk up the hill through the plaza, up the hill to the right, and the castle's entrance is right there.
If you take the train to Windsor from * Waterloo station, it goes the long way around and goes to another station in Windsor that's farther away. We learned this all the hard way :) Oh well, there was a restaurant with an ability to get a taxi near that other station, we try to stay low-stress with damage control. I went the bus the first time when I was living and working at the Girl Scout/Guide hostel for a while. Bus trip was good when the LegoLand crowd wasn't there :) Should be fine early morning.
My daughter unexpectedly loved Windsor, shopping was really good prices, sales were good in Sept, should still be fun in June.

Day 4: Tower of London on a Saturday will be more crowded. May want to move that to a weekday. Or maybe you'll make more friends that way :)

Day 5: Watch the transportation schedules carefully to and from Stonehenge on a Sunday. Many things are closed or limited on Sundays.

We had a variety of young women working at Pax Lodge, it's in Hampstead and they really liked Camden Market (buses 24 and 268 were the ones that went there and other rgreat places back in 2011). The popular thing for the girls to go do (besides pub quiz night) was to get a milkshake at Harrod's and to go to the M&M store in Leicester Square. Pax Lodge has events and tours if your granddaughter ever was connected to Girl Scouts as a Brownie Girl Scout or any age level, she may have an interest (it's also next door to Air Studios, where HP movie music was recorded, plus more).

The Treasure Room at the British Library is free, awesome, has a cafe' or 2 and a gift shop, the pub across the street was excellent in 2011, and it's right next to St Pancras Station (Eurostar), St Pancras Hotel (GORGEOUS, that's where we'll go to tea some day), and the clock tower was in a Harry Potter movie, then next door to that is the King's Cross station with platform 9 3/4 and a new gift shop. Every bus in the city seems to go up to King's Cross so it's super easy to get to with an Oyster card.

Kensington Palace doesn't look available for those dates for tours.

We went on the London Eye at night, I felt like it took us farther away from the sights, and there was no map to show what we were looking at, so it wasn't my favorite thing to do.

The thing I would add to your itinerary would be a boat ride, and that's how I would go to Kew Gardens next time. Overland train to Kew was odd, train stop was not helpful place, bus not easy in 2011, maybe the boat is more fun :)
And be SURE your mobile phone will work over there (don't believe salesmen, just people who did it), Google Fi/Project FI has others confirming that my phone WILL work there next time, same price as home, that's a big deal.

Have a great time!

The recommended way to the Harry Potter studio is, as Nigel stated, train from Easton Station to Watford Junction ( Oyster cards are valid for this) and shuttle bus from there. The bus runs every 30 minutes.

https://www.wbstudiotour.co.uk/getting-here#ID-c45147dee729311ef5b5c3003946c48f

We just return from London and seven nights at Number 63 B&B. Great place, great location.

We took the train from Paddington Station to Windsor. The transfer from the first train to the second train was very easy and the train station is easy walking distance to Windsor Castle. We had no problem.

We took a boat from Westminster Pier down river to Greenwich. We followed the Rick Steves' walk in the London book and visited the Observatory. If you like science, it was a great treat. My husband thought it was a highlight of our trip to London. We used our Oyster Card and took the train back to London (I think Victoria Station).

When you go to Westminster Abbey, the Churchhill War Rooms are very close. Definitely worth the walk and time.

Be sure to check out the Sunday Roast. London's food was not that great but the Sunday Roast was fun. Go early for the best selection.

Thank you all for the wealth of information! I will use it to fine tune my touring plan.

Yes, I did mean train to Watford Jct (after taking the tube to Euston), then the bus to the studio. I have timed out my travel segments so as to arrive at the studio at 11am. We have noon entry tickets. I'd rather be early and have time to look around the entrance shop, find the loo, etc before going in.

Thanks for the suggestion, I think we will move our Tower of London area day to Tuesday Day 6 to avoid the weekend crowd and then maybe Borough Market.

We plan to only do the highly recommended London Walks "Jack the Ripper" walk, but thank you very much for the heads up about the museum. We will be sure to avoid it.

I checked the time of sunrise in June and although we will not see the sun as it's rising, we will get private time within the stones before the site opens to the public. It will be quiet and peaceful if not actually dawn. Its a trade off I'm willing to make- we can doze on the motorcoach on the way and I don't have to try to drive on the left side!

And thank you for the Windsor travel information. UK trains are many and complicated! And I'm glad to hear Number 63 is a good choice.

You may enjoy having tea at the Orangery by Kensington Gardens and Hyde park. We had tea in a lovely garden conservatory and it was reasonably priced.
When we were in London there were ticket booths near the London Eye where you could get half-priced tickets to the theatre productions. The Mousetrap by Agatha Christie is a great classic and many of the musicals are outstanding. We saw Mamma Mia and Wicked and they were amazing. Or you could check online for theatre tickets and get them in advance before you travel.

On the day you go to the Tower of London (note: I highly recommend booking your tickets in advance), I would consider walking across Tower Bridge as it is a nice walk and then going to Borough Market. I make the Market a must do on each trip to London - it is fun to walk around, sample treats, and then pop into the pub that is right there for a pint. From there it is a nice walk along the river to Tate Modern and London Eye.

For tea, I would recommend The Orangery at Kensington Palace. Really lovely tea and you can walk around the ground before and/or after tea.

If you want to see a show and are not super picky about what you see, there is a TKTS booth in Leicester Square. I have used it and got really good seats to see Once a couple of years ago.

The easiest way to get to Windsor is by train from Paddington Station. Paddington Station is a four minute walk from Number 63 B&B. You will change trains in Slough, it’s just a change of platforms easy, it’s a total of a 35 minute ride from London. As you exit the train in Windsor, turn to your left, walk up to High Street and there across the street is the castle.