Thanks JS, that seems to work!
Not sure at the moment if I'll implement it, as we're already using QP6 for all Voice traffic and QP4 for all Voice-Signalling traffic. So, if I mark the whole 'Voice' Vlan as QP6 both RTP & Signalling will be treated with the top priority, not necessarily something I'm looking for.
One question though, assuming the phone sends through a frame with a dot1p value of 7, what will the switch do with it under default configuration?