I assume she is no longer alive, otherwise you need to remove this thread about her.
The marriage is :
Oct/Nov/Dec 1949
Norwich
Ref 4b 1295
Doreen Cowan / George A L Mountain
Do you know if she was a spinster when they married , or if Cowan is a name from a previous marriage?
If it is her maiden name, you can look on FreeBMD for births with surname Mountain and mothers maiden name Cowan, to see if they had children. As they are likely to still be alive (if there were any) then the names cant be posted here.
If Cowan is not her maiden name, then any births will show what her maiden actually was.
You may therefore need that marriage cert to ascertain her fathers name.