Ventajas
I worked as a part-time Customer Service Associate in the Cardiff call centre when I was a student. There was an awesome working environment--nearly everyone was cheerful and friendly all the time, the team leaders worked really hard to make sure everyone felt valued and had incentives to work hard, benefits were very good and the pay was about 50% more than similar jobs. The training was ongoing and very comprehensive, and it was easy to contact management staff in case of queries or problems. I really don't think you could beat it for a part-time job at uni.
Desventajas
The minimum part-time hours were 15/week, which is quite a lot to do alongside a degree. I'd suggest quitting early in your final year at uni to preserve your sanity and not get too stressed. Hours were slightly less flexible than you'd expect from a similar job, but not unreasonably so. When I left at the end of 2006, a lot of extra products were being offered but the staff hadn't been increased significantly, so it got very busy and hectic; I don't know if this has now been rectified.