First Home Improvements

I have been phoned regularly by a company calling itself First Home Improvements for a number of years. Despite entreaties to them to leave me alone, and regular complaints to the Telephone Preference Service I have been unable to get them to desist from contacting me. I have no idea what it is they are trying to sell me. As soon as you ask for their telephone number or for more details of who they are they ring off.

Anyone got any suggestions? Pay the directors a visit? Their offices?