Well now we know the two names appear in 1701, I can only proffer William Drummond of Hawthornden 1585-1649.
His translation of St Ambrose`s 4th century hymn appears in RCH (No 4):
O Trinity, O blessed Light, O Unity most principal, The fiery sun now leaves our sight: Cause in our hearts Thy beams to fall.
Another translation of this hymn by Neale has been widely printed, but for Drummond there would have been a dearth of Scottish music outlets in the C17 and onwards.
The chance of the Playfords acquiring William Drummond verses would seem slim, and similarly it is surprising that two people called Flexman, a pretty rare surname, were writing religious verse probably 100 years apart.
Julian's Hymnology seems to confirm that it is William Drummond that we are looking at. There is a surprisingly wide variety of hymnodists and psalmodists represented in The Divine Companion. I... more
It seems Drummond mostly wrote on non-spiritual themes, but some poems with Christian content are in his Urania collection. Maybe you could find your Playford text in this, or via the indexes of... more