Hi Helen - The marriage does seem to be missing, I think young John is registered
Ledbury, and William in Newent, I imagine you have been here
http://www.forest-of-dean.net/to see parish records, but they only do those parishes that overlap into Herefordshire. If you enter Sarah
Wheeler in the 1841 census there is only one and the birth year is spot on, she's in
Hereford with probably a widowed mother Catherine and younger siblings.
I imagine there is always a chance they didn't marry? If they did I doubt if they married very far from
LedburyWatkins throws up too many to make a guess. Good luck Fred