It doesn't make sense to say it's not his "natural" singing voice is my point. It's not affected or accented, it's just a falsetto, which many singers do, including him, on various solo efforts/beats he's made before. So many singers sing in falsetto for certain songs/portions of songs in fact most of the ones that pop into my head right now do it, it's a singing technique is all, doesn't make it any less "natural". Nor does it make it copyright of Thom Yorke (who doesn't use it all the time anyways).
It's not his use of falsetto that I'm saying isn't natural. It's his accent and singing style in general.
The thing is, I quite like some Bombay stuff. But his unnatural voice irritates me. I'm bot saying he's wrong to do it. Hell when I sing I use a bit of an accent. We have the same problem of coming from the south of England and if we were to sing in our natural voices, we'd sound like posh wankers.