I noticed today that Ancestry has added the 1939 Register to it’s collections. It was previously available only through Findmypast, and then only if you had a yearly subscription. Month-to-month subscriptions couldn’t access it.
This is kind of a big deal, if you are doing any sort of research in England and Wales during the WWII period. The most recent census available is 1911, so this may fill in some gaps for you. It’s also unique as a census, because it was later updated to include surname changes when women married.
Caveat: People who are still living have been redacted, for privacy reasons, so if you can’t find someone it may be that they’re still living or only died recently.