So had my bike checked today at dealer, and it appears to be the floating disc making the noise. My noise is more of a 'tick' actually than a 'clunk', whereas per the videos posted in this thread you can hear it's a definite clunk. We compared it against two other bikes there, an M Sport and Sport, and the ticking noise from the floating disc was the same. However, Service Manager told me to keep an eye on it and if there are any problems they will review again during Run-In-Service time. All in all, I came away happy that other bikes were the same, so fingers crossed nothing bad develops.