Ian,
Pete Scott from Hull, who some of you know, told me a couple of days ago that he had just seen a Ring Ouzel at Brompton, near Scarborough. Bird has been present for some time. .
Looking further, I came across a website "Ring Ouzel Study Group" www.ringouzel.info 2017/18 winter sightings and it appears there have been quite a few in the country recently, mostly near the east and south coasts, but including several in Wales.
So, given the recent weather, the report from Pont Llanio doesn't seem as unlikely as all that, and well worth a further look, I would think.