you get the fake host when you are auth'd (logged in) with the service, setting umode x without that doesnt do much.
you could react when your host is changed, this is raw 396.
a quick example:
Code:
raw 396:& wiebe.users.quakenet.org is now your hidden host:{
  join #chan1,#chan2,#chan3,...,#chanN
}

I have not tested it, but it should work