If we want to pronounce it properly we do it "Papa" - "ka" - "nga" - "horo" "horo".
I'd predict people who want to mangle it will probably go for something like "Paper" "kanga" "hoaro" (with a hard g like in kangaroo, argh) and leave the last bit off.
Paraparaumu gets called "Parrer Pram" by people who don't pronounce their reo. Not all of whom are pakeha I might add.