Yes you are in your right to cancel however, you can arrange check over the car a day or two before making payment. You are also protected upto the point prior to entering your PIN. If you choose not to enter it and walk away and the dealer will have to refund your payment within 5 days. How much of a faf this will be if the dealer plays funny buggers is another matter!
This is more or less what I have done in the past. As soon as the car has arrived with the dealership, I’ve been and checked it over before the they did their PDI. Then, when I’ve agreed, I’ve paid by bankers order and taken delivery a couple of days later.
I have arranged to check before PDI this time and will give it a quick once over before entering PIN as usuall 🙂