I stayed in London with Theresa and George for 8 days, and it was lovely! Every morning, George would help me plan out my day's adventures into the city, and, upon request, would cook me a hot English breakfast.
The house itself is a walking distance away from Greenwich for a day trip and also walking distance from the Lewisham Station (the rail will take you just about anywhere).
It was a fantastic first time in London, and I'd recommend Theresa and George to anyone passing through London.