Dear Deb
I see what you mean I just did a quick surname search on the Cornwall Census, 1841, 1851, 1861, 1871, and 1891 looking for Penfold's, Pinfold, Penfield etc. nothing in Cornwall as far as I can see.
I see one of the references Catherine found was in Devon, so perhaps it is Devon that they came from. I am sure the marriage certificate will help put you on the right track and then the 1901. I know you can browse the birth references on Ancestry as well as FreeBDM for those later years.
Good luck you will track them down I feel sure.
Kind regards,
Pat