I bet you'd get feck-all discount on an RS3 - A £40k "virgin" RS3 might see you with a GFV of £24k, but lets say you need to add £5k of options, and you're talking £20k lost. Chances are though, you'll have some equity over and above GFV, you'll likely end up losing £17k.
Take a £35k R (with options), and it'll come in at £30200 to buy with broker discount, likely be worth £17k at trade-in, £13200 lost. Is the RS3 worth an extra £3800 over an R? Probably!