I would be surprised if Motability offered you the car for £13,000, going by my previous offers to buy I would say they will still want around the £17,000 mark, they say that they look at a long term average and ignore sharp spikes/dips in residuals.
You are probably right, however, due to Mitsubishi announcement price have dropped dramatically.
Unfortunately I have suffered a brain injury and occasionally I get confused and often say the wrong thing.