mtDNA haplogroup U5b2c seems to most likely have an origin in Iberia probably during the LGM. The fact that the two Mesolithic hunter-gatherer samples from La Brana are U5b2c1 and the fact that U5b2c seems to have a very western European distribution today give strength to this possibility. Here is a good derscription of the distribution of U5b2c and it's subclades today.

''U5b2c has an age estimate of about 15,000 years based on 20 FMS samples. It has been found exclusively in western Europe. There is a one U5b2c* person with ancestry in Ireland.
U5b2c1 has 6 FMS samples including 2 from Spain, and one each from Ireland, England and Germany. One of the Spanish samples is from ancient human remains. Sanchez-Quinto et al. reported a FMS test result for the 7,000 year old remains of a Mesolithic hunter-gatherer at the La Brana-Arintero site which they identified as U5b2c1. Behar et al. estimated U5b2c1 to be about 4000 years old, although with large uncertainty in the date, while my age estimate for U5b2c1 based on the six modern FMS samples is 5,700 years. The La Brana-Arintero sample is at the upper end of the Behar uncertainty range and this raises the question of whether haplogroup ages might be older than estimated by Behar et al., and perhaps the slightly older estimates by Soares et al. might be more accurate. But it is not possible to reach conclusions from a single ancient DNA sample. The presence of U5b2c1 in Ireland and northwest Spain might be indicative of early population exchange between those areas.
U5b2c2 has an age estimate of 4800 years based on 20 FMS samples. This group includes 4 people from Ireland, 2 from Scotland and one each from England and Sweden. It seems likely that U5b2c had its origins in an Iberian or Franco-Cantabrian ice age refuge and arrived in the British Isles at a very early date, based on its frequency and diversity in Ireland.''


https://www.familytreedna.com/public...ection=results

I would not be surprised at all if U5b2c shows up among more ancient Mesolithic hunter-gatherer samples from Ireland, Britain and Iberia once more are tested. Indeed it could show up anywhere in western Europe it seems.

http://dienekes.blogspot.ca/2012/06/...-arintero.html