Currently in London and have come across some new-to-me info:
The Courtauld Gallery will be closed effective Monday, September 3, for at least two years.
The Design Museum (now near Holland Park) is very interesting. I didn't see the fashion-related special exhibition, just the donation-requested permanent display. It took me about 4 hours, but I read everything. http://designmuseum.org/# You can wind your way through Holland Park afterward; It's not Kew, but it is nice.
Also relatively near the Design Museum is the Leighton House Museum, the final home of the artist Frederick Leighton. £9 (£7 for seniors). He was very fond of Middle Eastern decor, and the tiles alone were worth the price of admission to me. The removable furniture from the house was auctioned off after Leighton's death, but they've had some success buying back several pieces, and some others have been copied from photographs. Quite a lot of Leoghton's artwork is also on display. I am not a fan of "House of xxxx" attractions, but for me this was very enjoyable. https://www.rbkc.gov.uk/subsites/museums/leightonhousemuseum1.aspx
The Tate Modern has an interesting special exhibition on Picasso in 1932. £22 (seniors £20), not including the £4.50 audioguide. That seems pretty pricey, but it's not a small exhibition. With the audioguide and reading all the posted text it took me over 2 hours. Recommended for Picasso fans. I enjoyed despite not being big on Picasso, but it helped a lot that I took advantage of a £10 deal for the first Friday of the month. No more of those; September 9 is the last day.