Chris:

It's been mentioned before, but I'll put it in again.
Frank Hennessy's "Celtic Heartbeat" usually includes a couple of Welsh songs in its 3 hour run on a Saturday night. It remains available for 7 days on the 'listen again' option, and a full playlist for the programme is also available at the same site:
Celtic Heartbeat with Frank Hennessy

CHEERS

Nigel