Hi all,
Had some trouble activating the game myself because of an issue with the cd-keys and I thought I'd share the solution in case anyone else is having the same problem.
When I entered the cd-key during installation Steam gave me a message saying I had entered a key for an add-on an should activate the original product first. As it turned out, the two keys I received had been swapped around —
when I entered the activation code for the Elite Regiment the installation proceeded as normal.
Hope this helps anyone if they're having problems.
Hussarknight