Don't be afraid when you read "20min tube ride from the city centre". Unless you want to go out at night, Agri and Roger's place is easily accessible (you can explore the whole city with the Northern line!).
Most of all, you'll feel immediately at home there. I enjoyed really confortable nights in that room - it is really intimate and cosy - and nice mornings watching the squirrels flirt with the birds. A perfect Airbnb experience!