Irish Proverb 207 - Seanfhocail Ghaeilge 207

This has nothing to do with the translation, but I have been noticing in most of the audio recordings, both here and in Buntús Cainte, that the "bh" or "mh" lenition is frequently pronounced more as a slurrring "w" sound.  Originally I was given to understand (from the "Teach Yourself Irish" book I bought, which a friend told me I would never learn Irish from) that "bh" and "mh" made a "v" sound, which they seem to in itrailing positions, but in initial or medial positions it seems very often to have more of a "w" quality.  Because I have heard this in both the Buntús Cainte recordings, which I assume use the Leinster/Dublin dialect, and in the Ulster dialect being used here, I am wondering if this has become somewhat universal for all the dialects?  Or does Munster or Connacht still use the initial "v" sound for those lenitions?  I remember from "Teach Yourself..." that medial lenited consonants are usually glided over, so I expect the "w" treatment there, but was surprised so hear the initial application in the recordings.  For example, I read "An bhfuil sé..." and expected to hear "an vwill shay..." but instead it comes out "uh will shay".

Clarifiction would be appreciated.  Thanks!

Dale D.