Hello everyone, a brief update on this. I sent off for the remaining Holywell record (Sep qtr 1858 Holywell 11b377), the GRO today mailed me to say "Each page in a register contains several marriage entries. The persons requested are on this page at the reference you quoted, however they are not married to each other".
So, that cancels that. The other Holywell record on Free BMD ( Dec qtr 1862 Holywell 11b 517 ) was definitely another family, so back to square one!
Wife Hannah's family at least seems to be quite clear - The 1881 census establishes that Hannah’s maiden name was Jones because she had two siblings, Robert and Mary Jones, conveniently (for researchers!) living with them in the Minera Cottage “Gottaea”. So I’m fairly confident that her parents were Robert Jones & Mary (nee Powell), as these siblings are listed with their father in the 1871.
The 8-10 year age gap between older Robert & younger Hannah as recorded in the 1881 and 91 censuses isn’t reflected in any of the marriage records I’ve seen so far, I’m wondering if there has been a mis-calculation? After all this, the Wrexham 31st May 1862 marriage still seems the closest - the names all match, including that of Hannah’s father Robert Jones, but there’s only a 3 year age gap between bride & groom, and earlier censuses show Hannah’s father Robert Jones was a circular sawyer, quite a difference from ‘engineer’ as stated in this marriage certificate. The Holywell marriage in the same year is the same - right father for Hannah, but not enough of an age gap.
It's interesting that the Wrexham marriage took place in a Registry Office rather than a church or chapel. The witnesses are Tho Walker (?) and Arthur Davies, no immediate family involved.
I'm thinking then, either some deliberate mis-quoting of age in either the Holywell or the Wrexham 1862 marriage documents, or their marriage took place much further afield - maybe Robert and Hannah met and married outside Denbighshire, there was a lot of migrating for work in the 19th century, and their apparent absence from the 1861 and 1871 censuses suggests this could be the case. But was it easy for couples to marry outside both their parishes?