In the characteristically Anglican series of books called the Alcuin Club Collections, an Anglican Scholar (American, I assume, because his degree is given as "Th.D") called Lionel L. Mitchell once wrote a volume called "Baptismal Anointing". In it he treats of the Baptismal rites in the Irish Stowe Missal, and comments that in "the Celtic Church ... olive oil of any form must have been exceedingly scarce" [I leave unexamined for now the deservedly long-discredited notion of a "Celtic Church"].
Splendid. What a good example of Anglican Common Sense. Anglicans set much store upon Common Sense. It's obvious, isn't it? No olive plantations in Ireland. The stuff must have been, for all intents and purposes, unobtainable. A sound basis for further scholarly conjecture.
But ... how about the use of wine in the Eucharist?
Where did those "Celtic" monks get that?
From the lush sub-Alpine vineyards of the County Tipperary, perhaps?
"Common Sense" can so easily forget that merchandise used once to travel so much more conveniently by sea than in lorries disgorged at ferry terminals.