Had an extended stay (circa 5 months) at Helens place for a business assignment and was the perfect central London base.
Immaculate apartment; clean, minimalist and modern. Great location, friendly concierge and the perfect host. Check in was a breeze, ongoing communication was slick and professional and any comms with Helen were uber responsive.
I stay in many short/medium term rentals through Air B n B for my many business trips and assignments in London; and I can safely say Helen’s place tops them all.
If I had one very minor grumble it would be that the street on which the apartment is situated is one of the busiest in Covent Garden and therefore footfall is heavy, even in the early hours of the morning, so it can be noisy when trying to sleep. But that is the dynamics of central London and, of course, prime tourist location in Covent Garden and convenient location more than compensates for this (very, very minor) grumble.
In short, if you need a central base for your London stay, be it business or leisure, then look no further and consider no other apartment. You will not be disappointed by either the accommodation or service.