Anecdotally I've heard of people getting discounts from the dealer by buying on finance, then asserting the right to cancel within 14 days* and paying cash instead. AIUI the dealer doesn't have to accept the cash, and could take the car back, but then they lose the sale, so they generally just suck it up.

(* https://www.carmoola.co.uk/blog/cooling-off-period-car-finan...)