Andy_Langton - 9:14 am on Apr 11, 2012 (gmt 0)
Local listings always seem to have been a tricky one for Google, since they rely on "self reporting" which, at best, needs access to a physical address. I can remember a whole host of different local listing quality problems over the years. Sooner or later, Google will fix it up (or you could report it).
But essentially your competitor is exploiting bugs in the system, and until those bugs are fixed, I don't think there's a whole lot you can do about it. There is the "report a problem" button in maps too, though.