In this November 2014 article, Katharine HIbbert of Dot Dot Dot mounts a strong defence of the property guardian concept whilst acknowledging the issues that may arise with less ethical service providers. London-based dotdotdot is unique (as far as we know) in being a social enterprise and requiring the property guardians to volunteer at least 16 hours per month. Rent is also payable. The article provides useful reference to other resources.