To answer your speculation about endurance, this 109 would have had to have a drop tank, and the raid would have to be on the ports of S-Wales. From there over to Ireland the distance is more or less under 100 km. That would still have been some 15 minutes to cover, or close to that.
The Spitfire would have been from 10th group, not so sure about the 109.
The British actually kept a squadron in N-Ireland during the BoB, but those were Hurricanes.
The LW actually attacked Dublin a few times (!!!), as well as Belfast, who got bombed quite a bit in 1941. It was a nasty raid and killed some 1000 people, but it was at night.
I guess one has to look at the film again and try to figure out, but thanks for the finding.