I'd definitely copy the complaint to the police. The most that they will do is pay the depot a visit and have a word, but that alone will make Sainsburys take serious notice, rather than sending you a stock letter and £5 of vouchers. I took this approach with a Stagecoach driver who cut me up and told me to 'piss off'. Plod paid the depot a visit, driver now has an official warning on his record.