Thank you Carole -- it's complicated!
I have looked for a marriage between a Gething and a Walklate without success. Of course, the mother may have been married before - so her surname at marriage would not be the same as her maiden name at the registration of a child.
In addition BOTH surnames could easily be mistranscribed.
I am stuck! I agree with your suggestion of obtaining the birth cert of the child registered at the correct time as per birth date in 1939.