Thanks for all the responses, especially Gibb Sahib's, which was the only one that directly answered my question.

With regard to imitating the Jamaican accents, no one has mentioned Nina and Frederik, who, as far as I'm concerned, sound wonderful, and as far as I'm aware, they were never accused of being patronising. Also, the vast majority of British singers sing in an American accent (going back to the first Rolling Stones songs), and do not get accused of caricature (I've never heard anyone claim that Adele or the Stones are patronising black Americans), so I don't see why it should be any different with the Jamaican accent, provided the singer has listened very carefully to the original and made a serious and genuine attempt to get the accent right. I always try to sing every song I sing in the original accent, by listening to authentic singers and trying to imitate them perfectly, and if I don't feel I can make a good fist of the accent I just don't sing that song in public. To me I am paying tribute to a culture by singing its folk songs in the original accent, not caricaturing it. And if you object to that, you should object just as much to Mick Jagger's or Odele's accent when they sing their blues or gospel-derived songs, because I suspect that's also the reason they sing those songs in an American accent - as a tribute to the culture that most influenced them musically.

FWIW, Jamaicans have in the past shown appreciation for my rendition of mento songs.