Exactly that, the screen price is already loaded with £5 -£700 part exchange allowance. If you got £2k off last time then I dont think you need advice on discounts.
If you have cash then buy private, buy with FSH and ensure that all consumables (tyres, brakes, battery, exhaust, wiper blades are in good nick as to fix the lot is around £2k and are rarely covered under warranty.
Cars over 7 years are difficult to finance from the dealer side so you could get a better deal with cash if you are looking for something pre 2005.
If I had cash I would go the auction in Manchester, Haydock or Leeds and bag an ex lease bargain.
Finally make sure if you get finance and want to pull out early, I would check that there is no early repayment charge or similair administration levy that will wipe out any saving or discount you made by taking this route.