Its standard practice when manufacturers need to dump cars before a facelift.
As someone has said, once the stock is sold off, its removed from the scheme.
That is just the way cars are sold. Motability know this, the manufacturers do it all the time.
Nothing you say or do will change it.
Its not as if you are buying a Motability vehicle, it is a lease.
Usually these deals are discounted AP and if you are quick, can grab one while the stock is available.