I've never heard of anything like this, but it'd be worth sending the university an email asking. If you're looking for an MSc in a different field to your undergrad, then it wouldn't be worth doing an extra year at university with your MSci if you know you want to change course/uni. If you're looking for it in the same field, your MSci will usually cover all the stuff offered at MSc, allowing you to go straight onto a PhD if you want to. You'll also need to consider the financial implications of doing an MSc on top of an MSci, so I'd steer clear of doing two masters courses.