i would recomend that you have the timing belt changed every 55k but they will last up till 70k , 60k seems to be the mileage that most have it done , but not all vectras have a timing belt !!! some such as the 2.2sri150 have a timing chain !!! hope this helps
All Vauxhall 2.2 petrol engines in Astra and Zafira have a chain. The Sintra and the Omega are belt driven as they were fitted with what was in effect a bored out version of the X20XEV which was belt driven.