We are a family of 5 so we needed the extra bed. The kids were all in one bedroom. The cot (that our son slept on) was actually very comfortable. The mattress was dense and provided great support.
We used a local little grocery store called Shepherds and we loved it. Fresh bread at night and in the morning. Cold meats, free range eggs, milk, ice cream, wine and beer. Zero degrees restaurant in Blackheath had great food.
Several days we walked through the park to Greenwich observatory (amazing pictures there and you straddle the hemispheres) and then down the hill to downtown Greenwich where you can embark on the river tours. Since this is Zone 3, make sure you know and understand the public transportation system. You can get anywhere you need to but some ways are faster and some are cheaper.
Our host Claire was very helpful and available to all if our numerous texts and questions and we were grateful to have her and the packet of information she put together at our disposal. Overall we enjoyed our stay very much.