Thanks Manish, exactly what I was after.
The only issue I have now is when selecting the template to use. If I select my vCenter, I'm unable to see any templates for use to add into the catalog.
I gave the vCD service specific permissions to the template but still no joy.
*EDIT*: I had a thought, so created a blank VM in vCenter and it shows up when importing in vCD. Can vCD not understand template VM's? Presumably I'd need to convert the template to a VM and then import it?