I can think of a few other possibilities - all from Ireland - but if it's not any of these, I think I'm done with this.
I seem to remember "The Matthews Brothers" singing "The Lark" in St. Andrews Folk Club, would have been early 1970s. I think they made 1 or 2 LPs around that time.
A group called "Tara" who played mainly on the continent may have recorded it.
I used to have an LP record which featured 4 acts from Dublin around the late 1960s. Not at all sure about this, but I have a feeling that Al O'Donnell may have sung "The Lark" on one of the tracks.
These are no more than suggestions which might jog your memory, Gordon. Don't think I can add any more.
Best of luck, Kenny