Maybe he's trying to protect (or hide for tax or creditor or other issues, not that I'm suggesting he is) the home address, possibly with the company connection, is it the registered office of his company, you can check here...
http://wck2.companieshouse.gov.uk/09b447f2d3ca 6478587dca9884c1d464/wcframe?name=accessCompan yInfo
He is the owner of the flat so can have access to whichever bit he likes in accordance with the tenancy agreement and other application laws and guidelines.
I can't see you could do anything unless he was interfering with your post which would be an offence in itself.