Thanks Heather,
The 1801 baptism is most likely the correct one as Edward Lewis was born in 1801. His stated birth place, Holyhead, may have been a reference to the nearest large town, both Holyhead and Rhoscolyn are on the Holy Island at the tip of Anglesey.
I'm basing the 1801 birth date on the information which he provided in the 1841 and 1851 census responses, but this does conflict with his death in 1875 where it is said he was 76 years of age, giving him a DOB in 1799 (more confusion - my head hurts).
His address in 1851 is Llidiart-Y-Gwenyn, Llanllechid, which doesn't appear to exist nowadays. I looked for it on Google Earth and ended up in the mddle of a harware store's yard at the end of Cilfodan Street, Bethesda. Perhaps that hamlet was removed to make space for the hardware store.
The Jones's may also have lived there at times. In the 1871 and 1891 census responses, J.O. Jones and family were living at 56 Cilfodan Street, Bethesda, but Cilfodan Street nowadays appears to have no more that three or so houses. If the street numbers did run up to the 50's, then that would have placed them in the middle of the same hardware store's storage yard.
Thanks for the Margaret Roberts information. I read that the Ogwen River, which flows through Bethesda, also flows through Llandegai. I wonder if Edward Lewis went courting in a row boat.