Not meaning to burst any bubbles, but the majority of your commercial DJ's have nothing to do with the songs that are being played on the radio, regardless of the country. That's what Music Directors are for I'm afraid. And in a commercial setting, it comes down to who your sponsors are, and what connections they have to major labels.
And even in independent stations, where DJ's get to actually program their shows, it all comes down to 'rotation lists'. I used to volunteer at an indie radio here and worked in developing their rotation lists - so basically of all the new music we'd get, the Music Director would listen to, figure out what was the best (rotation A), what was great (B), what was good © etc etc. Then DJs were told that in any hour they'd have to play x amount from list A, x amount from B etc.
It rarely has anything to do with a DJs preference on radio I'm afraid.