If the show is not available as a podcast but only as a live stream replay, you can use recording software. This is legal for "time-shifting" (recording a broadcast to listen to later) as per the Betamax ruling, provided you do not distribute the file.
Because Kiss FM is a global brand with specific regional iterations (UK, Romania, Australia, etc.), the "Fresh Top 40" content varies by location: : kiss fm fresh top 40 download