Domain names investigation

Someone has taken our .[login to view URL] domain name. In order to build our case before approaching the naming body in the UK, Nominet, we need to prove that the person who has registered our name has registered thousands of other names -- lots of which belong to other companies. He is very clever in that almost all of his names are unhosted so reverse IP address lookups etc won't work. Basically we need a way to find out what names he has registered in the past. If bidding please provide some very brief detail on how you might accomplish this. Thanks for taking the time to read and bid.