Hi Abigail,
I too, have been looking at the Jacques/ Jaques for quite some time( seems to be spelled both ways by those ancestors and relations of ours).
The Jaques- Robert, William, Sarah and Thomas of South Australia and Adelaide ( our Jacques who emigrated) are linked to Charlotte of Port Lincoln, if only by marriage. ( Found an article in a newspaper about her origins). However I think they more than knew each other!
She and husband John Black ( your tree) had son James who married Maria dau of William Jacques. Rumour has it they were cousins and related but am not sure how. I do consider that this William is the one who arrived with Robert.
Robert Jacques who is definitely connected- married to Ann in London and as it seems his parents of same. I have a signature or a Charlotte on a marriage certificate for I think, Robert's sister- my connection, who arrived two years after him along with his wife Ann and Thomas, however am not sure which Charlotte this is and if it is one and same as your Charlotte. It is possible of course that some lived in Ireland while others lived elsewhere such as London perhaps for work . I think ours were servants and stonemasons.
I am also wondering if those in Wiltshire are also linked in some way as they are linked with Sheffield as are other family members .
I have found some info on the London lot which seems to fit, There was also a Joseph Jaques in SA who I think is linked somehow as he is in the same area of Truro in the 1800's however don't know anything of his background.His woife came from near Sheffield.
John Black is also linked with Thebarton and the railway in Adelaide and William Newman J - Robert's son was at the same area as well.
Most SA jacques have been found to be connected.
Would like to hear from you- can you email me?