So yesterday i was in birmingham all day installing an SDSL line and moving all the voice traffic from there internet connection, to it all going over the private SDSL line direct in to the Data Centre.
They have a really nice network fibre backbone and some VLANs for DATA and
VOICE, they also have a really nice watch guard firebox (Which I like turning in to M0n0wall appliances :)) )
However the VLANS that had been set up where not true VLANs so the final solution i came up with was a static route for all voice traffic to go out over the SDSL Private line, which seems to have done the job perfectly.