DJ56 on Family Tree Circles

I have been researching my family history for some years and have been able to trace most of my ancestor lines back to the late 18th/early 19th centuries, in some cases back to the early 18th century.

However I am stuck on one line: one of my great grandfathers, Nicolas Augustin Joseph MARCOTTE (b France ca 1855) married my great grandmother, Julia GRAF (b ca 1853) at the Aenon Chapel, Church Street, Marylebone, London on 26 July 1879. His address is given on the marriage certificate as 30 Heshpool Street, Paddington, and his father as Nicolas Augustin MARCOTTE, landed proprietor. Her address is given as 397 Edgware Road, Paddington, and father as Jacob Friedrich GRAF, manufacturer, deceased.

There are no further UK records for either Nicolas or Julia, but I know that they returned to Northern France because their children were all born in Douai. Nicolas himself was born in Boulogne sur Mer. I plan, at some stage, to do some research in the French regional archives on Nicolas' ancestry. The regional archives for the Nord and Pas de Calais regions will be my starting point.

However, I have no details at all about Julia's birthplace, Jacob's ancestry etc, and really don't know where to start looking. There is a family story, related by my father before his death, that Julia was from Switzerland, possibly Lausanne. This seems a little odd as Lausanne is in the French speaking part of Switzerland, whilst Jacob Friedrich Graf is clearly a Germanic name.

Does anyone have any information that might help?