This special trip with my teenage son was our first visiting London. This flat was PERFECT for us.
Firstly, it's really spacious. Two bedrooms, each quite large. Because it's on the top floor, there was a concern that it gets a bit hot when we were out, but there is an air conditioner in 1 room and a fan/dehumidifer in the other, so it becomes very comfortable, very quickly. The kitchen and living/dining room really suited our needs. The kitchen is FULLY equipped: fridge, stove/oven, dishwasher, coffee machine and abundant coffee pods, and dishwasher. There's also a laundry washer, although we did not use it.
The location is super convenient. It's in a very quaint neighbourhood, with plenty of cafes and restaurants of all varieties, a supermarket, and an excellent Persian restaurant. It is a brief walk to the Underground (tube metro system), and I would suggest to download the app to help navigate and get you to your destination. It's also close to Buckingham Palace road, which gives you quick access to buses and hop on/hop off tour buses (you will need to buy tickets for these, but well worth it).
The flat is very fluid in operations: there's a clear instruction book when you come in, with instructions on the flat, as well as numerous places to visit, eat, etc., and maps of the surrounding areas.
You are very close to the majority of key visiting sites, so it's location really can't be beat. As well, it is relaxingly quiet, which is great.