I suspect budget features highly, the small time dealer juggling around with a couple of £1500 cars a week would no doubt prefer cash.

Go up the scale and finance becomes increasingly relevant, i would think an employed salesperson in particular is going to make any deal he can muster that pays him/her the most and it might be the case that finance and other packages net them more, i would expect a paid salesperson to prefer finance sale above a certain price level, where a sole trader just wants a profit however its arrived at.

Main dealers are essentially selling financial products secured on their new or 'approved used' cars. They like the commissions and incentives from selling finance. But they may also be keen to shift units to hit a sales target.

Unless there's a really good deal like interest-free credit or similar available, I would go on price and then discuss payment method.

Just make sure you get the best deal for you, not the one that the dealer wants to sell you.

Quite right to insist on setting the price before discussing payment methods. If you can pay outright, you should haggle for a discount. Alternatively if zero or a rock bottom finance rate is offered, you can bank your money and let it earn interest for you. Most dealers wont have a preference about how you pay for your car, a sale is a sale to them. You dont mention whether you have a P/X or not, but in general most used car dealers tend to do more favourable deals if there's no P/X involved, especially if your paying outright at the point of sale. My advice would be to visit as many dealers as you can this weekend, take your time deciding what deal offered suits you best financially, also don't be afraid to play dealers off each other. You're in the driving seat, It's your business they want, so don't be rushed into making a descision. Good luck.