I don't think you should change the spelling back, but I do want to point out that the film at family search was a transcription of the original land records book. The transcriptionist states it is a true copy with some exceptions "1. I have not retained, in most cases the antiquated mode of spelling."
The fact that every one of the Cornwell entries is spelled Cornwell would indicate to me that he may have standardized the spelling. Any of us who have looked at originals and "true" transcriptions know that any given name is seldom spelled the same during the 1600s.