I've found this - does it work here ?

"Agus cad é ba chiontaí leis sin," arsa Tom "ach is tusa is ciontaí leis sin"

Well, that means "What was the cause of that...but it's you that's the cause of that/to blame for that."

Your original post was: "Whose doing is it...but your own" (Who's the cause of it/to blame for it but yourself.), so your version needs amending to "Cé is ciontaí leis...ach tú féin/tusa." Which is not light years away from one of the versions I offered back then - "Cé is cúis leis...". My impression is that 'ciontaí' is used for "bad" things - which means it's fine here - whereas 'cúis' is neutral and can be used in any context - which means it too is fine here.

(Posted this last week. Must have forgotten to press 'submit' or something).

Go raibh maith agat

Is it possible to put the word - immediately - at the beginning of a sentence?
Here's the context -

Immediately on his smelling the cold air of this world, the child sneezed.

Chomh luath agus a bholaigh sé ar/d'aer fuar an tsaoil seo, rinne an páiste sraoth.

Mais oui. 'Chomh luath agus' lit. = 'as soon as'.

Merci - and would it be - d'aer - or - ar aer ? (in order not to use the definite article twice)

La suite .....

and it was naturally taken to be a good sign of having a clear head;

agus measadh gur dhea-thuar é léire intinne a fháil;

but the subsequent rapidity of his learning was truly amazing;

ach bhí tapúlacht ina dhiaidh sin a chuid foghlama iontach go fírinneach/go hiontach ar fad;

for on the very first day a primer was put into his hand

óir an chéad lá céanna cuireadh bunleabhar ina lámh

he tore out the A, B, C page and destroyed it

stróic sé amach leathanach na haibítre agus scrios sé é glan

as a thing quite beneath his notice. (I'm not quite sure how to translate this)

mar rud neamhfhiúntach ar a aire.