Personally I would have no further dealings with the dealer network at this stage.
I would write to the CEO at the registered address of the company in the UK and send it recorded delivery. Point out the fault(s), point out the dealer response and ask if that is the policy of the manufacturers. Tell him that you are writing to him to give the company a chance to rectify what is clearly a fault under warranty before you go to the Motor Agents Association, the SMMT and the media. Ask him if, in pointing out that a damper should not leak unless it is defective, he feels that you are being unreasonable. Name the dealership involved. Ask if ride/handling/safety issues are always treated in such a cavalier fashion by the manufacturers, or is it just the dealer chain which does so.
My guess is that the dealer will be instructed to immediately take your car in, replace the dampers FOC and lend you a suitable car whilst this is done.