There isn't really any mystery about why S Columba did not enter the church until after the Gospel of the Mass. For the answer, you only need to go to the Iveragh peninsula in County Kerry - that's the bulge sticking out into the Atlantic just South of the not always edifying tourist honey-trap of the Dingle. (Avoid the Dingle; go to the Waterville and Valentia Island area.) If you are a bookish sort of person, take the admirable Archaeological Survey of the Iveragh published by UCC. And, before you go, read my own paper in the Proceedings of the Royal Irish Academy, Volume 102C, Number 1, 2002. (You could do worse than to read the even older treatment in by Francoise Henry: Volume 58C, 45-166.) And let yourself be lured into crawling around the innumerable early Christian sites.
The Skellig Island (to which, as I recently observed, G B Shaw once had himself rowed from Sneem) is uniquely dramatic and - provided you are not easily seasick - a must, but you may be a little diasappointed by being made to wait before climbing to the top so that the previous lot of tourists can come down, chattering away into their mobile phones to their boyfriends in Barcelona. Go as well or instead for peace and quiet and visit Killabuonia and trace the buildings among the brambles on the hillside; and get a boatman to row you the few yards from Port Magee to Illaunloghan, excavated and spectacularly written up by Jenny Marshall White (for sale in the shops at Port Magee ... Magee was a pirate ...). Or during the spring low tides you can walk through the straights across to Illaunloghan, watching the scallops snapping shut as you wade past them.
What you will discover is that the stone oratories which survive in such abundance, often with 'Founder's Shrines' and standing crosses beside them, were very very small. And archaeology has revealed that the wood and peat oratories which preceded the stone edifices were even smaller. And yet, apparently, these chapels served large 'monastic' communities and very large lay districts. It is clear that entire congregations could have not got into these little buildings.
What obviously happened was that the bulk of the congregation was outside, and that even the clergy were outside, from the litany which started the Mass until after the Gospel. Then the clergy, probably not more than half a dozen individuals, went inside for the Holy Sacrifice.