Getting deperate with this one

Looking for a marriage for a Maude Nellie H Cox b 1878 Plymouth.
Family moved away from Plymouth to Sussex for the 1891 census.
Maude believed to be Isle of Man for the 1901 census (unmarried).
Her mum and younger brother living in Islington for the 1901 census.
Dad is .......... still working that one out.
I have looked on freebmd but there doesn't appear to be a marriage fitting Maude's full name on there, so her marriage (if at all) may have been registered under perhaps a slightly different name.

Another scenario is perhaps she married on the Isle of Man, that would be a bit more difficult to find as I don't know of a candidate's name for the groom.
Any help to perhaps finding a marriage much appreciated.
Ewan