You will find Welsh and English versions of the song at page 154 of 'Folksongs of Britain and Ireland' ed Peter Kennedy Cassell 1975.

In case that is difficult to find, the English words are:

My branch of joy, my armful warm
In all the world you have most charm
'Tis you that's caused both grief and pain
'Tis you that's stole my heart away

As I go walking at the dawn of day
My heart is sad, no longer gay
The little birds, I hear their song
For Liza comes a yearning strong

When in the garden I do stray
Among the flowers so sweet and gay
I cut the little prim-e-rose
For Liza fair my yearning grows

When I go walking at the close of day
My poor heart melts like wax away
I hear the sound of tiny strings
For Liza fair my yearning springs

O, Liza, come to me I crave
And place my body in some dark grave
I hope you'll join me my dearest dear
Unto the grave for I'm going there

Cheers, Stewie.