Hi and Welcome to RootsChat!
I cannot do the search for you (copyright issue).
On ancstery (

) select 1911 census search
Location "Hertfordshire" & keyword "Glenside" just happens to get an occupant of a house named such in the area you are looking, near to "the hospital" but obviously before it became . . . . . ( if it's the correct one )
This may help to narrow timescales when the maternity facility was functioning.
Quite common for "girls" to be sent to "mother & baby" homes.
Ray