I have the Welsh lyrics by Wil Hopcyn, and English translation by Walter Maynard in a copy from a book called Caneuon Cenedlaethol Cymru: The National Songs of Wales, Boosey and Hawkes, 1959. The book itself belonged to the choirmaster of a local Welsh choir here in Oz and I believe that it is a reliable source of information. The book also has the piano score of the music.

The English words are the same as those from The Contemplator site which masato linked to and start with " Idle days in summertime" with 2 verses only, but there are 4 Welsh verses.

The Welsh lyrics are the same as the ones at the "robokopp" site Penny linked to except for the second line in Verse 2 (8 lines per verse)

The robokopp version is:
Neu fi a'm ffydd yn ffolach,

but the book says: Neu fi yn wir sy'n ffolach

and the line in the second verse "Cwnn dy ben, gwêl acw draw" is written in the book as "Cwnn dy ben, gwêl oco draw".

The Welsh words which masato put in this thread are not the same as the ones at the "robokopp" site.

I don't speak Welsh so someone else will need to tell us what the difference is between these two lines, and whether they both make sense or whether one is full of typos.

You're right, Jon, the words you have are an attempt to sound the Welsh out rather than the real words.

Helen