I lived in this flat for six months and I miss it already.
It is perfectly located. It is a 5 minute walk to Parliament Hill. A 5 minute walk to the ponds and the rest of the Heath. A 5 minute walk to the Hampstead Heath Overground, several really lovely pubs, restaurants and far too many delicious bakeries. M&S is a short walk as is the Royal Free Hospital in case of an emergency, like one I experienced. I was treated at the hospital's Emergency department and was in/out in 2 hours.
The design of the flat was clearly given a lot of thought. The choices made for cupboards, countertops and exposed brick were a nice touch. I had guests for a few days that slept on the sofa, so having a toilet room right off of the lounge was ideal.
The bedroom had a large chest of drawers and plenty of built in shelves in the closets. I tend to go overboard in the wardrobe department so the large closets were great for my clothes. The bed was a comfortable double bed with plenty of good, quality linens and pillows.
My only warning might be to someone with limited mobility. There are concrete stairs that lead from the flat up to the street. Sometimes if they get wet, they may be a wee bit slippery and there is no handrail. But otherwise, it's perfectly situated.
Oh, and for a REALLY pleasant surprise, in the extreme heat London had a month or so ago, because the flat is subterranean it remained quite cool. I only need 1 fan going on the worst of the days and had no issues staying cool.