Hi Yr Elldee,
I think I have solved my St Ann's riddle ; the drawing I have, although it says it is St Ann's, built in the 1700s, and buried under the Penrhyn quarry spoil tips, is obviously that of St Tegai in Llandygai Village - although I still don't think you can see Penmaenmawr or the Great Orme, or the River Conway, from the church as the artist does!
Ecclesiastical records show it 'my' St Ann's was completed by 1807 (the year before Richard Pennant' death) and consecrated in 1813.
Apparently there is a large Pennant memorial in St Tegai's which also commemorates the building of the original St Ann's, and may show the church.
One remaining puzzle; I have an old map which shows a 'disused' church close to the quarry at Tan-ysgrafel. Do you know what that church was?
I think I have run out of sources for a drawing of the original St Ann's, but hope springs eternal.
Thanks to everyone who provided information.