Matteo's place is exactly as described. It's walkable to everything - including King's Cross/St Pancras - yet completely tranquil. I visited during a London heat wave, and was able to keep open the big windows on both sides of the flat, allowing a cool breeze to pass through. At night, the only sound was the birds in the park across the street.
There are two bikeshare stations a block away, and an array of fine neighborhood cafes, restaurants, and pubs.
If I had any complaint, it would be that the drains can be slow, which is also true of pretty much all heritage buildings in London.
Highly recommended.