My wife and I are visiting London this summer for a few days. I’m wondering if there are any music stores where they sell traditional instruments such as Irish flutes and whistles? There used to be one in San Francisco called Lark in the morning , it was fun to go in there and check out some of the instruments, although not all of them were the best quality..but there were some gems. I’m wondering if there’s anything similar in London?
Reading your signature, there may be an answer right there 
I thought: Mr. Gumby is saying that I am foolish or there is a music shop named Emersons, but doubt it is Hobgoblins, that sounds like a Harry Potter tourist trap. Thanks! I will definitely visit.
Hobgoblin also has a shop in Minnesota.
Hobgoblin is a small shop close to Oxford Street and Tottenham Court Road. Unfortunately not of much interest to trad Irish flute players but worth dropping in if you’re in the area. At the moment they have no secondhand flutes listed in their London shop - https://hobgoblin.com/secondhand/secondhand-woodwind/secondhand-simple-system-flutes/secondhand-simple-system-d-flutes
Nearby Charing Cross Road and Denmark Street has a few music shops selling new and secondhand instruments but mainly guitars. Have a look there and then wander around Covent Garden area, National Gallery (art) and Trafalgar Square.