Hi Christine,
Finally heard back from my friend. Sorry it has taken so long. She had some family committments.
No Joy on Lillian I am afraid. But I'll give you what she did find (which you prob already have)
Isadore James Knight Cohn married Annie Emily Amelia Harding in 1861 in Victoria ( she didn't mention a town)
The children she found are as follows
Lea Sophia B1860 Sand, Victoria
Edward Victor B1864 Cale, Victoria
Theresa Augusta B1867 St Andrews, Victoria
Flora Bertha B1869 Collingwood, Victoria
William Isadore B 1872 Collingwood, Victoria
After that they seem to disappear. The only child she found in NSW was
Silverton.C.Cohen B1884 Newtown NSW. He died as Silvester.C.Cohen in 1884 also in Newtown NSW.
She said there is a huge gap between William 1872 & Silvester 1884 & she's not sure where the registrations are.
The only thing I can think of to do now is to contact the NSW Registry Office directly to see if they can shed any light on where the registrations are for the yrs between 1872 & 1884. Maybe they were lost or destroyed.
Sorry things haven't turned up. But I'll still keep an eye out for things. Something might turn up somewhere.
Cheers Peta