Hello mate, completly up to you on the water pump but maybe for the sake of £20 it might last longer etc ect, but up to you bud. Water Pump £66 Tensioner £73 Idler £60 Are you replacing these at the same time as replacing a belt?? If so unless there leaking,squeaking etc they dont need to be replaced unless needed, our technicians only inspect at time of replacing the belt, as Toyota parts tend to last longer that Vauxhall, Renault etc that probably replace anyway. Cheers Sam