It looks like you need to take three exams for 2012, regardless of whether you're starting from scratch or upgrading:
I think the best option is to take the 2008 exams, then upgrade at a later date to 2012. This would involve taking five exams (two for 2008, and three upgrade exams). You'll have the qualification for both versions. This is my preferred route and was a key part in my taking the 2008 exams.
Additionally, studying for the 2008 exams will give you good preparation for the 2012 exams.