it can be used as an insult or as a general discription
Sid: "yeah mate i know em, proper bun heads"
Sid:"that boy Timmy he's a fucking bun head mate, all he ever does is blaze all day all night"
(adj.) Used to describe someone who is acting in a high, possessed, or Sherry-like manner.
Stop acting like Sherry! Your such a bunhead!