You have been given some good advice, about using we buy any car to get a base price for your car.
The general rule when I worked in the Motor Industry was 12k miles per year was average, so I would expect a 23 model to have about 36k on it.
I would also check on autotrader using the car you want to buy and see if any other dealerships are offering same car for lower etc that should give you a bit of bargaining power. Once you have a base price then you can go to the dealership and speak to the sales team, its easier face to face than on the phone.
Test drive the car, check the tyres, service history, mot etc and make sure the service history and mot are either done before you buy or have just been done in the last month. Anything you are not sure about ask, if the tyres look worn in ask for new ones. If you don't ask you won't get.
On my last car purchase I asked for 2 new front tyres, machine polished valet, and because the sales guy had a sense of humour a full tank of fuel. What I got was 4 new tyres, full valet with machine polish, 1/2 tank of fuel and a small bunch of flowers 😃I wasn't forward or pushy just a wee bit cheeky and got away with it.
I am and have always been called the negotiator when it comes to friends and family getting new cars (always used) but new to them.
Hope you manage to find what you want and happy motoring 😁