Possible cam belt issue?

Hi

I have a 56 plate Fabia 1, which I have just had serviced at Darlingtons in Harlow. After taking it away from the garage I've begun to hear a funny noise. It doesn't start straight away but roughly 10 miles/25 minutes into the journey I can hear a bit of a squealing/loose noise when the engine is idle, and up to about 1200 rpm. I've had a look under the bonnet and it sounds like the sound is coming from the cam belt.

Does this sound like I need a new cam belt or is it possible the people at the garage didn't tighten something etc? Shouldn't they have noticed this when inspecting it?

the car has done about 34000 miles and is 4 years old.

Many Thanks

Alex