As far as I remember (I haven't heard it for donkey's years):

Midsummer's Eve it fell on a Saturday,
Sue and William went to be wed.
They had music played by a fiddler,
"Let's go dancing" William he said.

CHORUS:
They danced, danced, danced around
Danced, danced, to the fiddler's sound.

Midnight came and "Stop!" said the fiddler,
"Dancing on a Sunday wouldn't be right."
Sue gave a laugh, "Don't care if to hell I go,
"I'll find another fiddler tonight."

He went off and left them a-grumbling,
Then another fiddler came along the way,
"You'd like to dance and I'd like to play for you,"
Tunes he played both merry and gay.

"Stop!" cried the dancers, "No" said the fiddler,
He carried on in spite of all their moans.
They couldn't stop their jerking and a-stumbling,
Then in a flash he turned them to stone.

Stanton Drew in the county of Somerset,
That's where the devil played at Sue's request,
They paid the price of dancing on a Sunday,
Now they are standing all at rest.

Don't know the author, and I'd be about 90% certain from the style of it that it is not traditional.

Hope I have all the line breaks right.