Excellent location - convenient and safe. Concierge on duty. No access to building or lift without tab on key. Muzaffar greeted us in the lobby and showed us around the flat as well as how to use the thermostats and appliances. There is a small grocery and a pharmacy around the corner, and Tesco is about a 7 - 10 minute walk on Edgware.
The flat is just a couple of blocks from Hyde Park, and 10+ minutes to Marble Arch Underground.
FYI - the least expensive way to Heathrow is the Underground with 2 changes. We had also thought of using the Heathrow Express from Paddington Station @ £22 per adult (2 of us - children under 16 are free). However best for us was Uber - door to door was £29 for all!