My wife, three daughters (12,15,18) and I stayed at Charlie's for a few days in August (our first Airbnb). Though we never actually met Charlie (he was away), we spoke on the phone and exchanged several emails. He was very helpful and flexible about arrival and departure times.
Charlie has a lovely period home, however it's probably not suited to those who are less mobile. It has quite steep, narrow stairs and you spend a fair amount of time going up and down them as kitchen, bathroom, living room and bedroom are all on different floors.
There are also quite a few personal items, ornaments, pictures, etc around the house, which make the place very homely, but perhaps not ideal if you have younger inquisitive children.
The neighbourhood seems quite fashionable, and there's plenty of nice little boutique shops, eateries, and bars around the place. Charlton Place is a short distance from the main action, so its quite quiet. Occasionally, after closing time, you'd get the odd loud voice walking down the street, but nothing to worry about.
Blackfriars Bridge is about 3km due South, so certainly walkable, but with Angel Tube station just 5mins around the corner, we used that everyday to get around London. It also meant that after a busy day seeing the sights, we knew we only had a short walk from the Tube to get "home".
If we are visiting London again, I'd certainly see if Charlie's place was available for another stay.
Neil