It's a lovely car and looks very well kept. At that price, you're waiting for a specific buyer imo. Someone who's looking for a 320d M Sport and knows a very clean and well kept example when they see it.

You've obviously spent a bit of money on it lately (refurb, service, tyres) but they're a sunk cost. They're effectively worth zero to the average buyer, who doesn't appreciate that they are saving in the long run if they buy yours.

I've got the same car and I wish you the very best with the sale. It's a beautiful car.

Why not keep it? Seems like there's plenty of good years left in it?