Hello Harry, I am researching my step great grandfather and in the process I have found he is linked with the Hankinsons and so I have a lot of information. Firstly I don't have any info on the family tree below your mother so that's (you are) news to me. Secondly Bertha's father was named 'John Henry Cust Hankinson' and I have identified 4 of his children (Gladys, Kara, Bertha & Edward) I suspect he also had Caroline but she died a spinster in 1902 and I haven't yet been able to place her in the family. Thirdly John Henry Cust Hankinson's father was Captain Edward Mitford Hankinson. Joined Royal Navy as a 14yr old, saw action in the Crimean War, repression of the slave trade of Africa, an took part in a expedition to Greenland. Decorated with 2 medals. I have other info on him. A lot of info on the Hankinsons can be found in "Records of Early Riverton & district, published for the centenary 1837-1937. (I have a copy) Your great grandmother Phoebe Ann Bertha's burial details are here:- http://www.southlanddc.govt.nz/cemetery-search/CemeteryRecord/7772.(youhttp://www.southlanddc.govt.nz/cemetery-search/CemeteryRecord/7772.(you will find others there as well) My interest is in Phoebe Ann Bertha Young as she became by second marriage to Dr James Young. Phoebe's eldest brother was my step great grandfather.
So, I hope that is something of interest for you. Whereabouts do you live?,have you any brothers or sisters and do you know anything about your mothers siblings and their marriages/children?