This might seem a bit mean on your part but even if the car is ready for collection, your contract with Motability hasn’t started. The lease starts on the day that you enter your PIN.
If you have been told to self-isolate or, God forbid, been hospitalised by the virus, the dealer will have to wait.
As a first time customer you may not know that some less scrupulous dealerships have taken paperwork and entered the PIN, triggering the lease. Customers have found faults or problems and had difficulties with the dealerships.
Keep your PIN in a safe place at all times.