No luck. I've just tweeted Caryl Parry Jones and am now hoping she'll reply.
In the meantime, I've run into another puzzling bit in the same episode. Here's the phrase...with the questionable word bolded:
Fel arfer yn y bore oedd credu pennau (?) dwrw yn y carchar oedd pobol yn cael i gadael allan o celloedd i fynd i ty bach a rywbeth a felly a cu das lubercost
That bit in bold sounds like
ah kee dahs lee ber cawst
but I've been unable to figure out what is being said.
Again...apologies for not including a link to the sound but BBC has pulled the podcast episode. If it helps, I've discovered that in the bit I'm currently working on, a man named Emrys Roberts is speaking about what he remembers of being imprisoned with Mahmood Mattan on the day he was executed (grim, I know)