Did your Uni openly advertise that they will let you do single modules or did you have to approach them and ask about it? This is such a good idea.
It was reasonably hidden in the website but it was there. You need an Institution which offers modular study (in real terms, not just on paper) and which offers co-curricular modules. Also, you need to find courses which aren't likely to be full to capacity, as they'll be able to fill their empty places with flexi students. Those which turn away students due to limited places well not be able to do this. This doesn't always mean the courses are not as good as the places which are full, it's often a funding issue or aspects of halls places, exchanges, etc. which mean one university with a perfectly might not be full. Mine ended up with empty places because they refused so many applicants at audition. They were oversubscribed with those desiring to enter the course.