Lastlid, that link and the quote is taken from a website of someone who makes money doing such reports.
To the best of my knowledge UKBA DOES NOT require such formal reports.
Neither is there anything in the immigration rules suggesting that.
These people do charge quite a significant fee for making a statement about accommodation in relation to the housing act.
Under normal circumstances unless the sponsor is renting a room in a multi-occupancy residence or is normally classified as a lodger, then such reports would not really be needed.
I stand to be corrected, and would appreciate anyone posting a link to either the relevent UKBA guidance or to appropriate Home Office immigration rule.
Until then, this is totally unfounded weasel word advertising taken form the website of a private business and is not a specific UKBA requirement for the granting of a visa leading to settlement.