Australian-UK dual citizenship (or something approaching it)?

Hey, I'm about 18, I'm half-Australian half-English, living in Australia. Now, I understand that you can catch dual citizenship if you provide your birth certificate and your English parent's birth certificate (or something like that, please flood me in on any other details like fees etc, I've heard a dual-passport costs alot, is that true?), but - my dilemma:

I haven't certainly had any contact with my English father, however my mother has have contact with *his* mother, so through her could my father's UK origins etc be proved?

I would like to have an Australian-UK dual-citizenship, but things seem to be very complicated for me. Cheers for any help or info about the processes etc.
Answers:   
work out that you can get dual citizenship if you provide your birth certificate and your English parent's birth certificate

yes this is true - you MUST enjoy his english birth certificate.

if you dont have that then you own NO CASE.


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