£20k is rather optimistic if you look at the prices for the older model from 2018 in higher trims (GT Line). And that’s not PHEV. But that being said: i’m no expert. I just had a look at autotrader and HonestJohn (https://www.honestjohn.co.uk/used-prices/Peugeot/3008/?q=GT+Line), which shows the old model at around 30% to 35% depreciation after three years, not 57% (that particular model was £26000 in 2018 new).
I’m actually surprised that they charged you for a colour, may i ask what you were looking at? A pearlescent paint (i think it’s the white)?
Also, my numbers earlier of course would need to be adjusted for the GT225, i was under the wrong assumption there, so do take that into account.
For the Tekna:
https://www.honestjohn.co.uk/used-prices/2018/?q=Tekna
I do think around £15k-£16k is not unrealistic after three years, but again: i’m neither an expert, nor in the position to give financial advice. It still would be a gamble, especially if the used car market doesn’t calm down.
What i’m wondering: does it need to be an SUV? Because if an Estate would do, then you’d have considerably more options (like the SEAT Leon Estate PHEV).
Prior: SEAT Ateca Xcellence Lux 1.5 TSI DSG MY19, VW Golf GTE PHEV DSG MY23
Current: Hyundai Ioniq 6 Ultimate
Next: we'll see what's available in 2028.