Tony, I think that you've hit the nail on the head when you said that Charles was illiterate. He would have spoken his name, the clerk would have written what he heard, and, especially if he knew about the illiteracy, would not have bothered to ask to check if the record was correct.
Name spelling was a fairly fuzzy thing - after all, they had no reason to think that anyone would be looking at the records again, except maybe to prove parish membership, or somesuch. Watch the ages in the census - some people age by 6 or 12 years (other numbers are available) in the 10 years between census takings, but often were mistaken. Imagine the conversation on the doorstop when the census taker finds that the form is not complete - "Husband, how old is your mother?" - he'd guess.
These days people accuse them of lying, but for centuries there were more important things to worry about. Before the days of official BMDs, etc, the only people who worried about the registers were the assorted Churches.