Yep, Tesco's in Wales advertised 'caws Cymraeg', that is, "Welsh speaking cheese" and had a till for people with 10 eitem neu lleu, that is, 10 items or lice.

I was just reading about the New Year's well-water custom and associated song from Pembrokeshire with the burden, "Sing levy dew the water and the wine". The question is, is levy dew "llef i Dduw" (exclaiming to God) or the French, "lever Dieu"? The French is entirely plausible, given the social history of South Pembrokeshire.

Perhaps the 'folk process' is even more inclined to happen, and more rapidly, where songs, stories, et al move between linguistic communities.

sian