Just to add I have researched the Wills and Quin families extensively on behalf of this search (creating a working document family tree on Ancestry in the process), and have not as yet found Ethel Wills (or Quin) on the 1939 register - crucial, as Pauline indeed suggests - so before anyone starts lots of additional research, please feel free to ask me (by DM?) what has already been found.
Added: I've just looked at my Ancestry research tree on this particular topic which contains 84 people and more than 230 records. I'm definitely not infallible, but we don't want people going over all this ground again.