Sorry folks to butt in on your forum.
Just to point out the passport issue.
I am an Australian with a British born father.
In Nov 98 I applied to the British High Commission in Canberra for a British passport. I got one. (Very prompt service too I might add).
Under "Nationality" it says "British citizen". As far as I can tell there are no proviso's or limits attached. Full citizenship.
Dad didn't register me with the British High Commision or any thing. I was born in the mid 60's but I don't think that had any thing to do with it.