Gunthwaite, I don't know if you took up my suggestion to contact the secretary of the Peterborough and District FHS, but if you haven't but intend to, it might be better to contact Alan Johnson, the society's archivist (same link as previously added on the Cambridgeshire thread). He is very knowledgeable, whereas Sadie McMullon is, relatively speaking, newer to the society and probably wasn't around when the Cathedral registers were being transcribed.