Give them until late Monday to reply to your email, then start your own topic on their forums.

If you want to try again elsewhere, the EU: Rome bundle can be had from Impulse or Steam for £14.99. I can't personally recommend Steam as my sole experience with it was dire beyond words. Impulse has worked fine for me for several purchases, and I contacted Stardock once and had a reply within a couple of hours on a weekday. There is a CD based version of the gold pack; might be worth asking about it at your local games shop.

You say you couldn't pay by credit card when you tried? That might be an important detail in unravelling what went wrong. It should pop up a little Paynova mini overlay inside your actual browser window. You then enter your details and click pay. My card has an added security feature on it so at that point I get a separate overlay to confirm passwords and such. Once that's done I drop back in at the order confirmed page. The game's immediately in my account page, and there's a confirmation email waiting in my inbox within a minute of placing the order. If that process couldn't launch then it's likely that something in your browser's security suite got involved and blocked the process, which would then have implications for the later transaction. If you got all of that and the site just didn't like your card then we're no wiser.