You only just recently bought that from a garage,
That's digraceful sell a car with something visably screwed,
I imagen they told you it was fully servised when you boughht it, surely they should have spotted that!
I would bring it back to them and get them todo a full service "again"
In the mean time as johnny said, pick up a new belt in halfords or somewhere and fit it yourself, You don't want that snapping on you all of a sudden!
Sorry for your troubles man!
Also mention to the car sales man that you are part of of 600 member car club who have bought a lot of cars of him in the past, and we are all waiting to see how he treets you!
Dan