Thanks but I'm already using the untrust virtual router to provide a default route for our "Home Use" Vlan.
What I ended up doing is editing the 'trust-vr' virtual router. (Under Network, Routing, Virtual Routing).
I changed the default preference of connected network routes to 10.
Then I created a default route to tunnel.1 with a preference of 5.
This didnt seem to negatively affect anything else.