You are legally bound to provide your insurance details, it's an offence not to. If he's asking for £480 then you're probably getting away lightly. You damaged his van, not the other way round. You are liable to be taken to court for the damage to his van, an alternative vehicle whilst his vehicle is being repaired and his loss of earning whilst he sorts everything out as result of your negligence. On what basis did you dispute his cost? Was it inspected by an independent engineer/bodyshop, or did you just decide it was too much? Advise him that you would be interested in paying for the damage yourself (if you are). Then ask if he would obtain a quote from a reputable bodyshop. However, regardless of whether you pay for it yourself or not, you must legally notify your insurer of the accident.