Hi again Philip
If you can try and get hold of a copy of the collection of family trees in T. Ceiri Griffith's book "Achau rhai o deuluoedd hen siroedd Caernafon, Meirionnydd, a Threfaldwyn". I found Henry Griffith at the top of chart [63], it doesn't give much more information on him than you have got already. He was known as "Cae Harry", (horse jockey), (connected to the family of Gwilym Williams,Criccieth who died in 1968 aged 86 years), baptised 1808 Bryncroes, buried 20/11/1894.
There is far more on Ellin since you have to go through around 10 charts to collect all her siblings. Her entry is Ellin of Brynhyfrd and Cefniwrch Bach, Criccieth baptised 27/22/1813 Dolbenmaen, buried 15/9/1907.
Ellin's parents on chart [57] are:
William Jones, Penybryn, Criccieth, baptised 13/9/1790 Dolbenmaen, buried 31/10/1845 Dolbenmaen aged 55yrs.
Jane Williams, Brynrefail Isaf, Garn Dolbenmaen. baptised 27/1/1790 Dolbenmaen, buried 20/5/1871 Dolbenmaen aged 78. It then refers to two other charts [15] and [271]. Two generations of her ancestors are to be found on charts [55] and [56].
They were married 21/3/1812 Dolbenmaen.
With regard to Henry Griffith since the search is in the Llyn peninsula area I would suggest considering making a donation to Yffor.com to allow you access for a month to that database which has the transcriptions for most of the registers for that area. Bryncroes for example goes back to 1732.
Glyn