Best bookstore for browsing middle grade children’s books

My 10 year old daughter and I will be in London in late November, staying in Fitzrovia. Can you recommend a bookstore with a good selection of middle grade books, particularly fiction? Her ideal bookstore would be something like The Strand in New York City, which feels vast and personal at the same time. I really like how the Strand organizes its collection into thematic tables that invite browsing, rather than endless shelves which are better for finding a specific book. Thank you!