I stayed at Juliana's place with a friend for a week. She and her niece helped us everytime we had questions and were very nice. The room was enough for both of us, the bathroom was a little small but private (I'm a small person so I didn't have any problems)... The room had a little fridge and water heater, very useful for breakfast tea or coffee. Juliana also left us little muffins and cookies in the room :)
Public transportation: there is a bus that stops near the house and takes you to a tube station (it's a little tricky at the beginning but Juliana helped us find the way)... and if you walk 10 minutes there are other bus lines that take you to another tube station. From there everything is easy. We recommend to use the app "citymapper"... with it you're going to find your way through London.
We really enjoyed our stay here and if we come back we would like to stay here again :)