That’s amazing , thank you very much !Welcome!
My advice, like some others here, would be to go for the 3.0d, ever though it is more expensive to run.
It is a smooth and powerful diesel and if driven sensibly is pretty efficient (I get average of 7,5 L per 100 km). I have driven the smaller diesels and generally not as good IMO, but of course more efficient and less taxes.
I would not necessarily worry about high mileage as long as the car has been serviced regularly, but my advice would be to get checked by a good garage before taking the plunge.
I bought a 2011 X250 3.0d (211ps version) with 220.000 km on the clock and previous owner claimed most was Autobahn coverage, confirmed in my opinion by the tell-tale stone chips on front of bonnet. I have since clocked up over 280.000 km and it is going better than when I bought it (thanks to a remap that has boosted torque from 450 to 600 nM and power from 211 to 250 ps).