Wow, what a place. I sadly never had the pleasure, being a West/South-West Londoner and only really making it as far as Camden in my teens. I used to live in Marylebone and there is still a fantabulous little bookshop - as far as I know - called Archive, which deals with a lot of sheet music and retains a piano. It's a marvel. Buried in the backstreets just south of Church Street market, and just thinking about it makes me want to bike into town and give them all my money.