We stayed at Kai's flat (ensuite double room) for one month after moving to London while we were looking for our own long term flat.
Kai and Whitney are such welcoming hosts, they always responded to our questions timely and were willing to help and make our stay as comfortable as possible.
What we appreciated a lot is their attention to the details — never seen such a detailed welcome pack describing EVERYTHING you might ever want to know about the flat and the surrounding area. In particular it was nice to know who would be our flatmates, what they do, when they are moving in and out, so you can be quite sure that you won't see random people in the apartment. Kai does well selecting the people allowed to stay there.
Speaking about the flat and our room, it was cozy and well heated, the bed was very comfortable to sleep on and Kai was happy with changing the bedding sheets and towels at our request since we were staying mid/long term. There is a kitchen, oven and washing machine you can use at your convenience sharing them with the other flatmates. You will also be given your personal space in the fridge and kitchen cabinets to keep your food separate from the others.
Location is convenient, e.g. you can get to Trafalgar Square by bus, to Shoreditch by Overground train, Canary Wharf by DLR train. Despite several smaller shops in close area there is also a huge Sainsbury's supermarket still in a walking distance which has any kind of food you might want, though along the way you might meet a few beggars asking for change. New Cross is perhaps an OK area but might not seem to be the safiest one, so don't forget to look around.
Overall we enjoyed our stay which felt like home thanks to Kai and Whitney!