The system in Scotland is somewhere in between - atleast in the ancient universities. I was accepted as a BSc Math student and took Math, Compsci and Psych first semester. Second semester I switched to BSc Compsci and took two Compsci and a generic 'great ideas' module. It was generally up to three subjects first year, up to two second year, then your degree subject in third and fourth year. But you could only do subjects in your faculty, most subjects falling into Arts or Sciences, with a few such as Math, Psych and Philosophy being part of both.

That said they did limit some popular classes to only people accepted to those subjects but Compsci wasn't one last I checked - though first year Compsci in my fourth year had tripled in size from my first year.