Banjo Ray is pretty spot-on, but I'd make a couple of points...

Huna blentyn yn fy mynwes Hinna blentin unn ver munnwess

I've never seen "yn fy mynwes". It's usually "ar", pronounced 'are'

And "ver" should be "vuh"

Also 'huna' is closer to 'heen-ah'.

Clyd a chynnes ydyw hon Cleed ah chunness uddew honn

Breichiau mam sy'n dyn am danat breyechiai mamm seen deen am dannat

Perhaps more like Breye-chee-eye, and 'dyn' would be 'din' (short 'i' sound)

Cariad mam sy dan fy mron carriad mam see dan ver mrron

Again, not 'ver' but 'vuh'

Ni cha dim amharu'th gyntun knee chaa dim ammharreeth gun-tin

Ni wna undyn a thi gam Knee oona inndin ah thee gamm

'undyn' = 'een-deen'

Huna'n dawel, anwyl blentyn Hinnan da-well ann-ooil blenntin

'huna'n' = heenahn

Hun'an fwyn ar fron dy fam. Hinnan vooeen arr vronn duh vamm

'huna'n' as above.

Makes you break into a sweat trying to think this out, doesn't it!? I think the Welsh National Gymanfa Ganu Assoc. in N. America is going to republish the (very) old phonetic hymnal - I don't know if they're thinking of doing anything similar for their folk book...

sian