I am not sure if Cash is King. I know that because of Financing the dealership gets a cut of the financing rate and thus can have more wiggle room in negotiating when the car is on finance.
Though look at new BMW / Merc prices in the North vs Ireland and you already have a discount on the price. Can often be better to buy a 2nd hand 1 year old car in the North and pay the VRT down here and still save or get a better spec'd car.
I was with a main dealer this morning pricing a January change of car for the boss, finance was quoted as 5.6% on a PCP, there was no discount if I opted for finance.
If I sell my current car and come all cash they will knock €2000 off my trade in price.
I also will not have the interest payment.
Cash is King.