They seem to have a large turnover in staff, least likely to know H stock (who's serving who here?) spoiled for customers ad overworked. I've heard most employees try to transfer to other London stores if they can. I also think they are the least consistent in terms of service, it can be awful but I have bought things there that couldn't be found elsewhere (like my Zenobie 90).
That does make sense - I think I was fortunate in my first experience there which was quite late in the evening in January and pretty quiet. The SA I met then was super friendly, knowledgable and happy to show me some goodies and talk about new upcoming leathers.
Ultimately, I decided to keep my focus and business solely at NBS because of the issue I mentioned above and for the fact they don't currently offer RTW and that I like a more serene shopping experience. But you're right, stock is super!