D5 Service intervals

I have a 2002 Volvo S60 D5 75000 miles, it has recently started to display a "Engine servive required" reminder, the cruise control will not work when this is displayed. I have my car serviced by a reputable garage not a Volvo dealership. I am wondering if there is something wrong or is this a standard reminder programmed into the car, can anyone also tell me the intervals for the timing belt change. Thanks very much, Paul B

Service Light 

Hi, Had a similar problem with my V70. Cruise came up on the display, but I could not engage it with the +/-; also the engine service light displayed on starting the car. Fault was the switch which drops cruise control out when the clutch is depressed. I believe the switch was wetted by clutch fluid when a seal failed. (Luckily the car was still under warranty at the time)

How much was the service if you don't mind me asking & was it at a main dealer ??

I had the same problem on a V70 petrol auto. It was the switch that disengaes the cruise.