I have been digging through the on-line records to trace Edward and Margaret's history. I mentioned previously the Edward was the illegitimate son of a David Davies and Elinor Hughes in 1810. I then focused on Margaret Davies. Her baptism record in 1816 showed that she was the daughter of Hugh Davies and Dorothy Jones of Tyddyn Iolyn. I decided to see who else had lived at that farm and did a 'House Name' search of the Census records.
The only hit was for the 1881 Census and showed William and Mary Jones and their family members, but lo and behold, there was a William Davies 14 listed as a Farm Servant. This would have been William's age at the date of the 1881 Census. On the image, his place of birth shows "Do Do", which also appears against the previous three entries all under under "Denbighshire Eglwysbach". My assumption is that William would not have completed the Census himself so any error would have been detected by him.
The only other record I have found is for 1901 where Charles and Ellen Roberts were residing there. Other properties around Tyddyn Iolyn include Pen Rhiw, Rhiw, Berllan Bach, Morfa and Dyto (1901) Fron Isa (1891). Do you know if Tyddyn Iolyn still exists?
Hugo, I have my fingers crossed for a good result from St Asaph.