Ubuntu – Install Ubuntu Desktop from ISO on XEN

I've got XEN Hypervisor running on Debian as my base system. I understand VNC and conceptually installing PV based systems on my hypervisor but I'm getting stuck starting from scratch on a ISO-based HVM.

I connect via SSH to DOM0, downloaded the Ubuntu Desktop ISO, created a volume and setup my configuration file like so (instructions from Ubuntu's website from Manually Installing HVM Guest):

builder = "hvm"
name = "ubuntu-hvm"
memory = "512"
vcpus = 1
vif = ['']
disk = ['phy:/dev/vg0/ubuntu-hvm,hda,w','file:/root/ubuntu-12.04.2-desktop-amd64.iso,hdc:cdrom,r']
vnc = 1

Than:

root@debian:~# xm create /etc/xen/ubuntu-hvm.cfg

Which returns:

Started domain ubuntu-hvm (id=13)

VM starts, now I need to run the GUI to install via VNC…but this is where I'm stuck: I'm connected via SSH or a terminal, there isn't a VNC application I can "Launch" so to speak, and the VM doesn't have an IP I can route to connect VNC (which is assumed isn't already running).

root@debian:~# xm vncviewer ubuntu-hvm
invoking  vncviewer 0.0.0.0:0
Error: Can't open display: 

I understand I can install Ubuntu server and add a desktop (and I assume a vnc server after the installation) – but this didn't feel right given they given instructions for installing HVM and connecting via VNC?

Do I need to do some sort of PV style installation of desktop…?