Celton on Family Tree Circles

I am having trouble finding out when and where Robert changed his name and any information to assist would be appreciated.

I know that he was an umbrella manufacturer and was born in London, England under the name of Eldridge. His mother and father were Robert and Mary, this info was obtained from his marriage certificate to Catherine Lennon in Melbourne Australia. On the certificate his name is Robert Elton and his parents were shown as Robert Elton and Mary Pryor (although, if the birth certificate I have found in London under the name of Eldridge is correct his mother was Mary Higgins).

I know that the name was originally Eldridge because Robert's son William was sent back to England to live with his Aunt and Uncle (Richard and Rachel Fitzgerald - nee Eldridge)and there was always a family story about a change of name from Eldridge to Elton.

I know a lot about Robert and his wife and children but not the reason for the change of name and when or where it happened. I have also not found a death record for him. There is a death registered in Hotham but after receiving the death certificate from Australia I have discounted it. The number and sex of his children are wrong as is the occupation.

Many thanks.