Matt's Knightsbridge apartment is superbly located near Harrods, and quite close to the Knightsbridge Underground station. The neighbourhood is upmarket and very safe, even at night.
The three bedrooms are spacious, and the kitchen and living area are also quite roomy. The only room that could be described as "cosy" is the single bathroom, but considering the location, this is a small inconvenience.
Matt was a considerate host, and met us upon arrival. He even agreed to postpone some urgent maintenance work on the apartment until the end of our stay, so that we were undisturbed during our holiday. We appreciated this very much.
There are some small supermarkets nearby; I'd recommend Waitrose for food quality and regular specials.
It is a bit of a walk to the Knightsbridge tube station, especially when Harrods is closed (they have their own entrance to the station), but don't overlook the buses as an alternative; we found the 14, 74 and C1 buses particularly useful.
Value for money probably depends on the season - we went in winter when the weekly rate was lower, and found it good value for such an upmarket part of London.
Overall, I thoroughly recommend Matt's apartment for your London holiday.