Sophie's place is great. A bit further from the city centre, but very close to buses and overground, which makes it easier to get around.
The flat offers pretty much everything you need (full kitchen, washing machine, iron board, etc). We stayed for 3 weeks, so she offered weekly cleaning, which was great for us.
The only downside is that the flat is the bottom floor of a family house (with very thin walls), so every morning you can hear the kids waking up for school and every evening it's possible to listen to the tv upstairs.
It's nothing that would ruin your trip, but something to keep in mind.
Sophie is also very helpful and replies to messages promptly, so i definitely recommend staying here!