Hi
I have just checked HALS for Herts marriages & Mary Ann Wingrove married William Jarrad of Horton Kirby Kent, 3rd July 1854 in Watford.
John Baldwin married Jemima Lovett both of Watford so he isn't your John at all. (Don't know why I didn't do it before

)
I think we can safely say that your John's wife was Mary Ann Nash although I do think he married an Elizabeth sometime between 1871 & 1881 but haven't yet found the correct marriage.

Let us know what other info you would like with regard to the Baldwin & Nash families if we can help further.

Maddie