Just out of curiosity.
The original southern course, back in 2009, was voiced by @Iestyn and Cat. I believe Iestyn is from Caerphilly and basically the course is/was how he speaks. I don’t know if there’s been any changes since then.
Aha, just got to Lesson 2 Level 2 and one of the narrators mentions he is from/lives in Ceredigion, so that explains it!
Helps me feel better about not being able to get ‘disgwyl’ in my head instead of ‘edrych’ as well as lots of others! 
Yes, they were living in the Rhymni Valley area when they started recording, but moved to Ceredigion later, and their Welsh altered a little after the move to fit in with the local area.