Different dealers have different rules but I’ve never paid an ap or deposit upfront, mostly because I’ve never been asked to buy if I had I would go elsewhere if and it’s pretty unlikely you paid a dealership say the full ap in advance and before delivery they ceased trading you could be right up the creek (unless paid via credit card with min of £100).
My dealer didn’t ask for a penny of the £2499 upfront and they later did reduce it to £2099 without me even asking and the order date didn’t change.