Terminating a VLAN tagged PPOE connection property on Fortigate 90D - Having problems

Hi all, 

Looking for some help on this one. I am trying to terminate a PPOE conenction on our Forigate. The connection has a VLAN tag and the only way I have got this to work is to create a virtual interface with the VLAN tag under the physical interface and terminate the PPOE connection here. This works and I can get internet access via this Virtual interface, however it is causing problems because I cannot ping this public interface externally (so having problems pushing DNS/services over this link).

If I try and terminate the PPOE connection on the physical interface (port) it fails (think its because i cant set a vlan tag here?) and it appears the only way to get this working is to set the physical interface as manual 0.0.0.0 and then terminate the PPOE on the virtual interface. Here is a screenshot of the current setup to give you an idea (ignore the mgmt vlan).

I feel like I am missing something here so any ideas would be appreciated. 

Thanks