DIY
www.honestjohn.co.uk/used-prices/
Put it in to we buy any car, cazoo, autotrader, motorway - any will give an idea.
If it’s any help last year I sold a 13 year old Honda Jazz CVT; WBAC valued it at £2500, I advertised it on EBay asking £3250 and got £3150.
Suggest getting a WBAC valuation and add 25% for a private sale.