Colin and Phillip, I'm researching MURLY/ Murley/ Murby/ Hurley (etc.) and will chime in here with my two cents worth. First, I found Phillip's terse and immediate reaction that 'his' John couldn't be Colin's John to be questionable. Possibly he is correct they were not the same person, perhaps they are, and beyond that, perhaps they are related somehow. From both your comments I don't see a direct connection to my Murly but I can tell you, I've found her surname spelled with multiple variations: Murly (in baptism record which I just viewed); Murby (in marriage record which I previously viewed); Murley (I think that was death record); then we get to the transcription errors, which have made it Murray, Morley, Murley, and even Hurley.)
As far as Catherine's cause of death .... death certificate stating cause as 'chronic diarrhea' - to me - doesn't totally rule out childbirth as a factor. Ex: A woman could have delivery by cesarian, develop an infection, linger for a month, with fever, etc., and then cause of death may be listed as 'sepsis.' Does that mean 'childbirth' was or wasn't a factor?
I'm not trying to be argumentative here, but one thing I've learned after doing genealogy research for going on 30 years now, is that you can't be rigid. And you can't get locked in on one spelling or one date for an event or one specific location of an event. You may have been told 'Grandma was born May 1, 1898 in Prussia' and her birth certificate (if one exists!) may give different day, or year' -- it may also be now described as a different country. Census entries can be particularly frustrating. 1895 census may list her as age 1; 1900 census may list her as age 2; 1905 census may say she's 7; 1910 census may say she's 15. After her marriage, 1940 census may say she's 33. Discrepancies occur because an older sibling with same name died (but you think it's 'her'); dad or grandma may not remember birth dates, or ages exactly; census taker may get ages confused when there are multiple children (particularly if the person providing info goes back and forth) and, when older, individual may not know, not remember, have been told incorrect info, or just 'shade the truth'.
And, Colin, I don't know if you're familiar with naming traditions, but there are some helpful articles available. My ex's family - it's 'tradition' (and has been for centuries) that the first born male child be named 'Karl.' When you have large families, that in turn have large families, and the are all living in same area, births are recorded in same place, it can be difficult to impossible to match up that 'Karl' that you found to the correct family. So, I'll caution you about jumping to conclusions about just 'who' that John Murley who married Mary Lock is.
It's possible that every "Murly" you find in Bridport was/is related. But it's also possible that the 'Murly's' aren't related to the 'Murley's' - or that every Murly is NOT related to other Murly's
In closing, I'll mention that I was researching yet another line. (Who really isn't important.) Found cluster of individuals with same surname (the usual variations in spelling, but that was consistent despite where any of them lived) living in different city. Someone who'd researched THAT line was adamant 'there's no connection between 'your x's' and 'my x's.' I just kept researching, adding all these individuals, even though they weren't linked ....and sure enough, I finally entered THE missing link - and connected the branches.
Also, out of blue, got a letter from a man in Canada, inquiring about my ancestors.
I'll now go back to looking for MY ancestor! Turns out, the branch I'm connected to 'fell off the family tree' ages ago - and he managed to link all back together -
It's helpful to keep an open mind.
So, I'll go back to looking for my ancestor. Good luck!