Did they give you a complaint reference number? Without that, you can't escalate it to the IPC. Not that the IPC will do anything as they are a bottom-dwelling organisation that was set up to protect their members profits at the expense of their members victims.
However, a formal complaint to the DVLA is definitely in order as you have the evidence of their deliberate non-compliance of the PPSCoP which is a breach of their KADOE contractual obligations.