Everything was nice and easy, and Philip was very accommodating - very flexible check-in (we arrived a bit early, but were nevertheless able to leave our luggage at the flat and pick up a set of keys even though the previous night's guests were still there); nice big room with access to a balcony; the neighbourhood is quiet and calm. We would recommend the little independent cafe 'Meet Me by the Baobab Tree', just a few minutes walk away, for breakfast (although the flat's kitchen is also available to use, of course!). The flat itself is a little walk away from public transport - but maximum 10-15 minutes (can be as little as 5, depending on bus times).
Altogether we had a wonderful long weekend in Berlin, thanks again Philip!