I recently came back from a 6-night solo retreat at the Hermitage, part of the Barn retreat centre, which itself is part of the Sharpham Estate.
The accommodation was excellent. It was a perfect mix of seculsion, with support if I needed it. The coordinators were kind and available but otherwise let me do my own thing. The space was beautiful, quiet (if you discount the wrens & blackbirds) and very conducive to going deeper. The views are wonderful. You can see what my daily routine looked like here.