Hi!
I really like this option to just ask for some artist and then Siri will play his most popular songs.
I just say: Play Busta Rhymes, Play 3oh3, Play Linkin Park, Play The Lonely Island and I have a quick "playlists" of their most popular hits and since I like them, I like everything what's popular from them.
But... maybe it's my American Siri or what, but there is NO WAY to just Play TINIE TEMPAH.
Can you say Tinie Tempah to Siri so that she understands?
PS To workaround this I just play some selected song like: "Written in the stars" and then just ask for more from this artist.