This is taken from the translation made by Niall Ó Domhnaill of the King of Ireland's Son back into Irish from the English version written by Pádraic Colum. I've managed to get hold of the first part (Cuid 1). If anyone has access to the second, I'd be very grateful, if I could see it, if that's possible.
He begins the story with a set formula that isn't in either the English or the French versions. I'm not quite sure how you would translate into English - 'Bhí sin ann'.
Here's the complete sentence -
- 'Bhi sin ann, agus is fada ó bhí'
Séamus Ennis starts his story with - Long ago and long ago it was, and I've recently heard exactly the same formula from Mike Burns, a Kerry storyteller who has gone off to Québéc - that's how he begins the story of the Fisherman's Son in Québecois.
The other important question I have, is this - Pádraic Colum said that he wrote down his version of the King of Ireland's Son, when he was in America, to stop himself losing his Irish. He said that he too translated it into English from an Irish text. Which text would that be? What Irish manuscripts would have been available to him in 1916? Would anybody know?

Bhí X ann agus is fadó a bhí.

A usual beginning of a story or fairy-tale.

I'd translate as: Once upon a time ...

'Once upon a time, long ago'? The Séamus Ennis version is grand, of course. Sorry, can't help you with the rest.

Go raibh maith agaibh.

Here's a short one taken from Seoda ár Sinsear - I'm not sure, but I might have posted it up before, but anyway, it starts like this -

Bhí fear ann fadó, agus fadó bhí,
Cheannaigh sé láí agus ba deas an láí í,
Bhain sé spreaibín, agus ba deas an spreaibín í,
Bhí neaidín faoin spreaibín, agus ba deas an neaidín í,
Bhí uibhín sa neaidín agus ba deas an uibhín í,
Bhí éinín san uibhín agus ba deas an t-éinín é,
Bhí drioball ar an éinín chomh fada le mo mhéirín,
Sin deireadh le mo scéilín 's nach deas an scéilín é.