Alex and Olga are amazing hosts! I really enjoyed my time in the UK. Their home is modern and clean and close to public transit.
Hackney Central and Hackney Downs are both 10-15 minute walks from the flat. From Hackney Downs, I took the Overground directly to Liverpool Street (15 minutes). From there, you can get to wherever you need to in central London. Alternatively, from Hackney Central, can take the Overground to Highbury and Islington (3 stops) and change to the Underground (Victoria Line), which can get you to central London. Getting to/from Heathrow takes ~1.5 hours, so plan accordingly.
Also, the 38 bus stop is 200 meters away. You can take it to Angel for restaurants and shopping. At night, the N38 drops you off at the same stop, so getting around at night is doable and straightforward when the Underground/Overground is not running.
The neighborhood is safe. A number of restaurants are a street away, including vegan/vegetarian. Less than a kilometer away is a Sainsburys for getting groceries, and, a bit farther away, near the Overground, is a large Tesco.
In terms of the flat, the photos are accurate. The back garden is awesome. The Internet is fast. The kitchen is well-equipped. The street is quiet at night, so easy to sleep. And the hosts are great!
Thank you again, Alex and Olga!