Is the MY error?

[Pam Downes]

I have certificates for James to confirm his parents as Caroline & Samuel - I guess their marriage certificate would be prime candidate.

Yes, and as pennydog has a church for you (post # 5) get a copy of the entry in the parish register from the relevant archives office.
Transcriptions - which is all you've seen so far - have been known to be wrong. And there are times when the vicar's writing is atrocious, and barely legible, so copies sent to the GRO are liable for mis-transcription en route.

Pam