gibjo on Family Tree Circles

My great grandfather, CHARLES MILLER, was born in 1851 on Gibraltar. His father, also CHARLES, pre-deceased his birth. He was married to Elizabeth (nee LONG)who returned to the UK and appears in the 1861 census under a new name of VOLL.
I have been unable to find any information on the senior CHARLES MILLER other than he was a Convent Guard (being the seat of Government on Gibraltar) He was born in England but I do not know where.(probably South East) I have no death certificate for him on Gibraltar.
I would love to know how to find out anything about him. If you can help, I'd love to hear from you.