Hi ponybun. Chanel New Bond Street is the flagship for UK, and largest Chanel in Europe if I remember correctly. I'd definitely recommend visiting for that reason alone.
When I visit London I prefer to shop at Chanel New Bond Street. I find it much nicer than Harrods and Selfridges. It's not crowded, and I have chatted with different SAs.
Thanks for the tip! I was just worried that with it being the flagship, it would get really busy and awkward. But if not, definitely destination of choice!