I had a quick look for them, but have not been able to find anything just yet, but mind you I only gave that a functionary glance, as have mainly been looking up the others.
I don't want to guess too much (for obvious reasons), but I notice that the 1791 marriage was at St Swinthin's church in Bath between Sarah Piper and John Hulme (bachelor and spinster).
Then the marriage for John Hulbert to Sarah Bennett in 1799 has them both listed as Widows
There is a Sarah Hulbert who passed away and her burial date is listed as 27 May 1793, St Swinthin's church Bath.
I am going to look for Sarah Piper's 1st marriage as well, but with the children born close by, the timelines in regards to the children etc and a lack of John Hulbert's marrying Sarah's it seems like a fairly strong match