Guest, ursa, was close, but the official words are:

There's a neat little lass and her name in Mari-Mac
Make no mistake she's the girl I'm gonna track
Lots of other fella's try to get her on her back
But I'm thinking that they'll have to get up early

Mary-Mac's mother's making Mari-Mac marry me
My mother's making me marry Mari-Mac
Well I'm gonna marry Mary for when Mary's taking care of me
Well I'll be feeling merry when I marry Mari-Mac

Now Mary and her mother are an aweful lot together
In fact you hardly see the one without the other
People often wonder if it's Mary or her mother
Or both of them together I'm courting

Well up among the heather in the hills of Benafee
Will I had a bonny lass sitting on my knee
A bumble bee stung me right above me knee
Up among the heather in the hills of Benafee

Well I said - wee bonny lassie where you gonna spend the day?
She said among the heather in the hills of Benafee
Where all the boys and girls are making out so free
Up among the heather in the hills of Benafee


Wedding's on a wednesday, everything's arranged
Soon her name will change to mind unless her mind has changed
With making the arrangements I'm feeling much deranged
Marriage is an aweful undertaking

Sure to be a grand affair, grander then a fair
Gonna be a fork and plate for everyone whose there
And I'll be a bugger if I don't gat my share
If I don't I'll be very much mistaken

Hope that helps, took me a long while to get my tongue around this song! (Unlike Clinton Hammond, GBS is my favorite band. I have it all :)