pon usually deisel enignes are totally scrap when the belt goes due to the comp ratio

not sure on astras obviously but in a escort deisel engine ya not only bend a few valve but ya actually reseat em in sideways and the other half sits in the piston

might be lucky though , that was what happened on me cousins engine though

diesels also need cambelts doing alot as they wear out quicker and risk fooking the engien so is done at some service times