I've read through the UK visa sites (and australian sites too) so many times my eyes are bleeding!

My basic story goes like:
My grandpa was born in Kenya in 1914 - His parents (at least his mother, we don't know anything about his father) was born in India (Damon? 1882)... We are fairly certain that Grandpa has/used to work for the British government in india/afghanistan at certain stages, even the BBC at once stage. (I am still fairly sure he was a british citizen, *somehow*)
My dad was born in Bombay, India, 1952, and they all immigrated to Australia in 1963.
As for birth certificates (god knows!) I dont' have them, neither do they. Records is the last of my worries at this stage!
The reason I want to go to the UK is to travel and work over several years, as I want to travel to the UK, then to europe, then back ot the UK, obviously the working holiday visa doesn't cover these time periods. Can anyone help? I was looking at ancestory visa as the most likely option. Grandpa was very anti-indian for some reason - So they left in '63 when indian became complusary in schooling. (So i'm told).
As I understand they are all australian citizens now (grandpa gets the pension)...... Dad's only 'evidence' of birth he has was a baptism certificate (!), and that's it!
Can anyone help with info?
Much appreciated,
Thanks
Aaron