It depends on your course. I think some of the business courses like the finance or law with management courses, you can't choose any modules in second year. But the rest you can.
In BAM, you do 4 compulsory modules, and then you choose 2 streams for the other 80 credits. In MAS you can pick and choose the other 80 credits from different areas. And I think you get a choice for a couple of the modules in some of the other courses too. I don't know much about combined honours though..