Thanks for your interest everyone, I'm very grateful.
However, the story may have moved on a way. It is possible that:
a) Phyllis wasn't English but Brazilian, in which case she might have got confused as to what surname to put where, and in none of her subsequent marriages did she call herself Cliffe!
b) It is possible that her marriage to Morton was annulled.
We are also now wondering whether she HAD to keep getting married in order to avoid being sent back to Brazil. It's a very obscure hypothesis, but not entirely out of the question, maybe?