I have stayed at John's with a colleague on a business trip. The twin room with private bathroom was perfect for us and the location too, since we were working at the closeby Crystal Palace sports centre. So I can't say much about the connection to London City, but what I can say is that our stay has been fantastic. John and Nathalie made us feel welcome and looked after - it felt like holiday homestay! John has provided us with all tips and information to reach their home easily from the airport, communication was easy and quick. The house is clean, tidy and warm, with a beautiful backyard. Nathalie has treated us with yummy breakfasts and lovely chatting, which also did John. Their son Marco even walked us to the sports centre on our first day and he's such a nice guy.
We loved the neighbourhood, great pubs, convenient shops and lots of restaurants. I hope we get the chance to stay at John's again!