hi Selena
I get your problem. Definitely straight forward if there's a name change!
If he was called Kenneth Cotton at birth though, do ypou know if he was born locally? The only births I can see for Kenneth are not in Lancashire. That may be because they aren't all online.
By this date thpough, if you look at the GRO birth indexes, the birth entry should give you the maiden name.
Then you can look for a marriage, for the two surnames and find the father's first name - and the mother's.
The To look through them with out going to a library, you need to be paid up to Ancetry - though you can look at that in a library online for free.
This one should be quite short, but I haven't got access just now.
Of course then you can get the full details by sending for the certificates.
Best wishes
Emms