I hope you have some success Hugo.
For reasons best known to itself Ancestry has thrown up another entry for Miriam Owen in the 1851 census. This is one I haven't seen before and looks very interesting. The household is:
John Owen, head, age 34, married, Fowl Dealer, born Dwygyfylchi
Jane Owen, wife, age 33, born Pentrefoelas, Denbighshire.
Keturah Owen, daughter, age 5, born Gyffin
Jeremiah Owen, son, age under 11 months, born Gyffin
Miriam Owen, sister, unmarried, age 20, general servant, born Gyffin.
They are all stated to be living in Gyffin village in the same household.
One reason I say this is interesting is that in a later census in 1861, Miriam Owen states she is a Fowl Dealer.
In the 1861 census John Owen and family (plus numerous servants) are living in 7 Mostyn St, Llandudno. John Owen is a grocer.
In the 1871 census John Owen and family are living in 8 Mostyn St and John is now a Game Dealer.
There is a baptism for John Owen in Dwygyfylchi on 10th March 1816 (born 27th February). He was the son of William Owen and Eleanor Hughes, abode: Pentre Felin. William Owen was a Blacksmith.
This fits with Miriam's father being William Owen, Blacksmith, per the marriage certificate. Also, in the 1841 census, Miriam is living with Elinor Owen who was her mother by the look of it.
I note the names of the children of John and Eleanor are very similar to those of Isaac Jones and Miriam.
For the first time a Family Tree has appeared for Miriam Owens. This states she was the daughter of William Owens bLiverpool (c1791-1877) and Eleanor Hughes (c1791-). Miriam is shown to have been born/baptised on 1 August 1830 in Llangelynin. The tree belongs to David Smith. There are a number of photos with this tree.
To be continued...