We could not be more delighted with the flat. We too have a relatively old home (well, by American standards) and could not pass up the chance to stay in a Victorian-era flat. I love the period details like the tinted glass block in the bathroom transom, the interior corbels, the picture rail, etc.
The location is ideal - enough outside of central London to be a good value, yet close enough by train or bus to be convenient to all the sights. The trains to/from Gipsy Hill run frequently, but we had even better luck with the buses from Crystal Palace.
Hint: Google maps was indispensable for step-by-step directions on what train/bus to take and where; download an offline map of London before you leave home to save data. Buy a SIM card from "Three" telecom, at WH Smith across from the Sainsbury's supermarket close by the flat - it worked flawlessly in my iPhone 5s.
The neighborhood is delightful - several supermarkets and many restaurants are very close by and convenient. We felt very safe - the police station is close to the flat. Our favorite moments included spotting the red foxes scurrying around the nearby streets!
We much preferred this historical, character-filled home over a soulless efficient new hotel room that would have soon faded into our memory. Rachel's service and communication have been top shelf - she emailed us local tips beforehand, and was very quick to respond to questions. She is a wonderful hostess.