Where had I heard that...

Oh, yeah. It was the Rubberbandits song Horse Outside.

"Giddy up now baby, bless my soul

I rode the fucker round a field back since he was a foal

He runs a bit like Shergar, and he jumps like Tír na nÓg

He looks like Billie Piper after half an ounce of coke

And the boys are lookin' jealous, as I lead yer one away

And just before I close the door I look at her and say

Would you be my girl, and she says I will of course

If ya grab me by the ponytail and ride me like a horse Ya!"

Yet, as far as jumping horses Tir Na Nog looked pretty average.