Lizzie
As far as I am aware the only criteria that Motability has are that the award has at least a year to run, so your new award letter should be sufficient for you to take out a new lease, just be aware that the DWP appears to be extending all awards that expire in the next nine months or so but they may assess you earlier than this.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems