Thanks so very much despair!! You have a very appropriate name for how we both must feel   

I've taken a look at your research and you're right that it would seem to fit with the Meredith. But yet again, they're very common surnames, well Lloyd at least, if they were uncommon names I'd be very much inclined to agree with you  

 It's a shame that there isn't the vital man- John.
Family lore which has thus far been spot on, says that John was Welsh (and so why I posted in here), and is supported by 2/3 census. I have gone through every single John Lloyd b 1864, including those born way out of census places and have found a few possible contenders. I'm currently trawling through these once more.
Even though the marriage cert should say deceased if so for the father (Thomas) was dead, I am now looking for contenders with a deceased father. This may help explain why John wasn't sure where he was born as they could've moved around a lot?  

I've found an interesting chap on the 1871 in Llwydiarth. (About 13 miles from 'Gillsfield') 
Ellis   Jones   Head   -   Male   34   1837   -   Ysbyty Ifan, (?)Denbighshire, Wales   
Margaret   Jones   Wife   -   Female   40   1831   -   Llangynog, Montgomeryshire, Wales   
Robert   Hughes   Son   -   Male   10   1861   -   Llanfihangel, Montgomeryshire, Wales   
Robert F   Lloyd   Step-Son   -   Male   10   1861   -   Hirnant, Montgomeryshire, Wales
John Lloyd Step-Son   -   Male   7   1864   -   Hirnant, Montgomeryshire, Wales
(Robert F seems to be in London as a bus driver in 1891)
No sign of this lot on the 1881 census or any baptisms for the children. Why is Robert a Hughes if he was Ellis' son?
Now I need the most important part of a marriage for Margaret to a Lloyd, or even better, some baptisms. No stronger a case than yours, or even possibly weaker, but a possibility?