Welcome to the club, Ian.
Once you have made up your mind as whether you are going to buy a petrol of diesel engined car and set your budget, I always look for the youngest car with the best service history and mileage and then take it from there. Having all the bells and whistles is nice, but not absolutely necessary, as some can be retro fitted.
When you have had a good look around, and armed with other information from XF owners, you will see the car you want.
Regards,
Peter.