Comments

Thank you for the confirmation that Mary SINGER was William's 2nd wife, that makes sense. I will certainly be having a deeper look into this tree.  

Looking at the Marriage Records for Huntspill on our site I see that a Mary HEMBERRY[sic] of that parish was married in 1792 so that probably rules out the Huntspill one.  Can you get any clues from the names of her children - could any of them be named after her parents?

Very helpful. Effectively the 1841 date of death is misleading and corresponded to a search I was undertaking, mea culpa. In fact I believe that she died in 1847 (burial 9 January 1847 aged 87 at Locking). This would tie in with the 1841 census record age-wise. Curiously the 1841 census result did not show up in my searches on Ancestry previously; however I have now found it and it confirms my previous supposition that Mary PIPE is the widow of John FOORD (dcd 1793) as she is shown as cohabiting with Mary FORD (25) and Charlotte FORD (14) who would be her grandchildren via her son, John FOORD (born 1792) from her first marrige.
This information doesn’t rule out Mary HEMBURY being from Meare as I had initially thought, as you so rightly point out baptism dates don’t neccessarily coincide with birth dates, however her parents married in 1769 which does pretty much rule her out.
Mary HEMBURY from Huntspill was born on or before her baptism in 1755 which makes her death in 1847 aged 87 a problem, as her implied birth date would be 1760.
It rather looks as though I will need to do a bit more digging although having taken your advice to look in the parishes around Burnham, Mark and Wedmore I have so far come up empty handed. The only Mary HEMBURY, baptised 1767 in Wedmore, appears to have passed away young.
I have also found a Mary HEMBURY baptised 17 January 1762 d/o William & Hester HEMBURY in Bristol, but this might be too far away.