Btw kingjohn, on the Celtic thing. While these lineages are very likely neolithic in origin, its dispersal might indeed be related to Celts (or para/proto-Celtic peoples). This is just being inferred, but on FTDNA Big-y Blocktree I can see the European individuals are all originally from Western Europe: Portugal, Spain, France, Germany, Canada and Brazil. There's Valerius, who's Bulgarian, but he shares a much more recent branch with a Canadian of French descent. Then there's my FTDNA y matches, who are all Iberian, and going by their surnames our original ancestor was probably from eastern Galicia or western Asturias, in NW Spain.
Keep in mind that, even though my branch is possibly the one found in the Indo-Iranian groups, the subclade itself has a TMRCA of over 5000 years, so it's possible that they belong to a sub-branch, and that I belong to another, and if that case it's perfectly plausible that mine is European, rather than Asian, too.
I checked those I2a individuals in Swat, who are with my E-Y31991 folks, and their haplogroup is I2a2a1b1b1. I2a2a1 equal to I-M223 and it's presence is also mostly in Western Europe, and less in Scandinavia. However, its TMRCA is even older than Y31991, at ~12000ybp. Its hard to know what really happened, maybe it's one of those haplogroups that were somewhere in eastern or southeastern Europe during the Chalcolithic and got picked up by early IEs and moved into Asia, but most of its surviving individuals stayed in Europe, and dispersed into the West for whatever reason (maybe the same as E-Y31991?)
It's a good thing I don't give uniparental markers much personal importance, because if I did I'd be pretty lost.