"A lot of English singers affect Oirish accents when singing songs from across the water"
Happens a lot with tourists here - never ceases to amuse the locals
I've heard Americans refer to Am-English accents as "Mid Atlantic" - in other words, neither fish nor fowl.
It seems to me that, if you wish to interpret a song and make it your own, you sing it in your own accent - otherwise, you are just aping the person you heard it from.
Jim Carroll