There is a tree on Ancestry which has Frederick Victor Bergmann marrying Gladys Dixon. It doesn't mention that he changed his name to Howard but the marriage in 1932 is under his new name.
The first child, John Michael, was registered in Hampstead Q1 1932
Second, Anthony George, Q3 in Hampstead. As George A in 1939
They are on the 39 register, but elsewhere.
David