There seems to be many issues regarding the installation of Ubuntu onto an XCP server and it not wanting to mount the Cd-Rom
After much mucking about I have managed to get this to work.
On the internet you will easily find half of the solution but when using XCP you have to make a second adjustment for it to work.
You must use an “Other Installation” template when creating the VM, if you use an Ubuntu related template it will not work.
When booting off the CD you must select F6 and turn off ACPI and NOAPIC
Once you have done this you should be able to continue the installation normally.
The only other note I have is that if you have issues running the live linux installer from usb you should use the “Startup Creator” from another Ubuntu installation to create the bootable USB as this can solve other issues as well.
I have tested the above method with both 12.04 LTS and 12.10 and can confirm it is working.