I Have been driving my Fabia all this week, and at the start of the week all was fine, but On starting it this morning the car has a really sqeaky fanbelt. Now, It was driven really hard last week (Like I Stole it ), would that have made it loose, and is that covered under warranty?

Doubt it but it should be easily fixed either by tightening it or replacing if it is worn out.

There should be some bolts you can loosen to adjust the tightness but I can not describe where they are. Also, from what I recall you have to hold it in place whilst you re-tighten the bolts.

Note if you dont do anything about it you may end up with a flat/broken battery or worse (happened to me!)