Please forgive me if I'm misleading you, but have you searched generally for William Ilbery? Was he a watchmaker? I have found https://collections.museumoflondon.org.uk/online/object/137938.html which mentions what might be the father, and a Swiss connection.Of course this could all be a co-incidence!Paul
Jorose's advice above is your best course of action. Bear in mind that 'Susan' might be an anglisised version of her first name. Any Swiss research will require her name and place of origin and/or place of birth. Once you have these, then come back here, put Switzerland in the thread title and there's a few of us who will guide you further.Good luck!Paul
In case you haven't seen this ...https://www.findagrave.com/memorial/126680056/william-ilbery