A4 1.9tdi noisy engine when warm

Hi, i've owned my 2002 model for the last 3 months with 98000 miles on the clock and have just started to hear a rattling/grumbling noise from the engine once it is running warm. It does not effect the overall driving of the car but the noise although sometimes disappears can usuallly be heard at idilling speed, it also gives out a screech whenever full lock is applied on steering. All temp guages / warning lights are normal and only thing that i have found in the way of low fluid levels is the power steering fluid at just above minimum on the dip stick.
I pressume that the timming belt would need changed as the service book reads that it was changed at 55000 miles,but i remember some years ago i had an old peugeot 309 and it made a similar noise just before the water pump failed and when i brought my A4 to my local garage and i explained my self diagnoses of the possible mechanical problem he just put his ear up to the engine and agreed with me saying that i was correct and went on to say that he could also hear a slight noise from the timming belt so i should get this changed at the same time (although i think all the belts now need changed anyway). The thing is he put a price on around £500 on the whole job but i was wondering has anyone else had this problem, any hints appreciated.