Hi Peace, just caught this thread. There is currently a study (it might have been published by now) into mitochondrial DNA (which passes untouched (apart from the odd accidental mutation) down the male line) across the UK. It's beginning to look as if the Welsh are descended from pre-Celts, i.e the stone age inhabitants of the British Isles, not just from the Celts as previously thought - who of course dwelt in these islands before the Romans, Saxons, Normans et al. Successive waves of invasion pushed them into the west of the country eventually - which explains the relationship between the Welsh, the Cornish (and the Bretons), whose languages are all Brythonic Celtic, and the Scots and the Irish (a lot of migration historically between these two lands), whose languages are Goedelic (Gaelic) Celtic.   Hope that helps.
!

Buddug