We stayed at Alton's for one week, and it was a great experience. The room is very comfortable (and warm for these cold days!), the kitchen has a great deal of things to prepare you own food, and the place in general is very cozy and tidy. Alton is very friendly and was always willing to help and answer our questions whenever we needed, and also acted as a great guide around Greenwich (BTW, a very interesting area.)
It is conveniently located 3 minutes away of Greenwich station, where you can take the DLR to Bank or the train to central London.
We would go back to Alton's if we had the chance to visit London again.
And we definitely recommend staying at his place!