Hi Wendy.
It was all a little bizarre as I dip in and out of the family's family tree as and when I have a little time. I just googled Willem's name and I saw your post re Enid.
I had researched Enid Webb as I knew that she was my grandfather's second wife. My grandfather was originally married to a Dutch lady and they divorced in 1924. Willem came over to Guernsey and had two children with my grandmother (out of wedlock) and then he met Enid in Guernsey and they married in Rijswijk on 4 January 1933. They had three children - Launcelot, Chloe and Herbert Reginald (Now dead - I don't think he was their natural child though). They are mentioned in a book called "Lihou Island - Never at Half Moon" by Robin Borwick.
They divorced on 30 May 1942.
I managed to track down Launcelot to 409 West Madison Street, Villa Park, Illinois 60181. I spoke to him on the phone and he told me a few bits and pieces.
Launcelot said that the children had a hard time during and after the war. They were taken into care at some stage. Enid went to France and apparently worked for the Germans in one of their camps. In 1947 she became involved with another Dutchman and went to live in London. This information came from Launcelot. I did write to Launcelot but never heard back from him. Chloe lives or lived (not sure if she or Launcelot are still alive) in the Netherlands. Her married name was Palm-Dekker.
As Enid was (I think) from Guernsey, you could pay for a family search using the Priaulx Library in Guernsey. I have used them in the past and they're efficient and inexpensive.
I hope this is of some use to you.