Aky answered very quickly and nicely to our emails.
I arrived a little late but it was not a problem since a late check in was possible. The appartment is very close to the transportation : there are bus stops (included night bus) and subways at less than 2 minutes by foot.
We had a small issue with the heater but this had been solved as soon as reported.
I will keep this adress in mind for my next trip in London.