TBH, sick of everyone saying you can cancel if you like
From motability “If you have placed an order for your car through a Motability Scheme dealer and have since changed your mind you must speak to the dealer directly to discuss changing or cancelling the application. Please note that your dealer may charge a cancellation fee in these situations.”
Obviously, they dont have to charge a fee, and VW didnt charge me when I changed, but its purely at the discretion of the dealer. Probably linked to model, extras, is it in build, do they have buyers waiting etc etc, but it is not a guarantee that you can cancel without charge.