I like your site layout, it’s very easy to use and I wouldn’t worry too much about the white space on some of the pages as its the content people will be after. A lot of people fall into the trap of filling every single pixel of ‘real estate’ on their site and users just end up confused.
One thing I would suggest is that you add “Football Manager” and “Worldwide Soccer Manager” into your tagline in the header because as a loyal Fifa Manager addict I always find it confusing when sites just refer to FM.
Also you link to “our forums” but it takes you to a different site. I presume this is also your site but its a bit confusing for the user to appear on a different site, you might want to put a little note explaining why the user is being taken to a different web address.