Conroy writes on Rootsweb about the mtDNA hg. of his father: H5k. There has been the answer of Gail Tonnesen and Ian Logan, i.e. the best experts of this matter. Of course Gail Tonnesen is prudent, considering only the FGS to say something, but Mitosearch (and what a pity that SMGF is out now) is plenty of HVRI with the mutation in 16304, and many will be H5, and from HVRI and II we have many who match these haplotype:
263G, 315.1C, 456T, 16304C.
At this point we should be sure about the haplogroup (H5).
Many of course are from the Isles, but this sample (Mitosearch TZZT5) from Poschiavo, Switzerland, but clearly with an Italian surname and an origin in the Ladin people, makes us think that also this haplogroup could come from the Italian Refugium.
Many are also from France. One says: "Haplogroup H5k Unknown - adopted - obvious Celtic physical attributes" (Mitosearch: D4EGW).
The haplogroup is found till East Europe, Turkey, and in Italy till Sicily with subclade mutations (DDAX7, TWREN, X7WTN). I'd say that it is the typical diffusion from the Italian Refugium.
H36a is testified only by Irene (Irene Pichler), then the Alpine zone which is for me the Italian Refugium. H36 is found in Finland, i.e. where arrived the most ancient people from the Southern European Refugia (Iberia and Italy).
H5k may be a subclade of the Isles.