Could be valve seals but unusual at that mileage. I would check the glow plugs, connect a meter between the feed cable and earth, switch the ignition to the glow plug setting and check the voltage, if all the plugs are working you should have 10-11 volts for about 30 seconds, if you have nearer 12v you have on or more failed plugs, no volts at all and you probably have a relay or ignition switch problem.

Classic symptoms of valve seal / valve stem / valve guide wear. Mechanical repair is the only cure. Left, it will get worse and cause valve seat wear (with loss of compression) in the longer term as the valves move around too much. The increased clearances in the valve stems / guides caused by the wear don't allow sufficient oil film to be retained for proper lubrication. In petrol engines it is also accompanied by an ingestion of oil through the stems / guides on over-run, with the attendant blue smoke.

I've also seen excess wear of valve stems cause them to break - resulting in a wrecked engine.

The classic cause is starting up at cold and driving off too quickly. i see many people in car parks who so obviously have started up with the clutch in and first selected - then, wooosh, they are off the INSTANT the engine fires. Bad, very bad.

Start the engine each time with no throttle and in neutral (though you may wish to dip the clutch in cold weather to remove the gearbox load from the battery - though I do not favour this, i prefer to get the 'box spinning too to get lube moving).
Wait 10 seconds before selecting gear and moving off. (I put my seatbelt on during this period).
Move off gently, and drive moderately for the first mile. Build up the use of power and revs.

This allows the oil to get moving before putting the engine under load. In particular it allows oil to get up into the cam cavities and to the turbo and start to do its work. Cams and valve gear are invariably splash lubed rather than pressure lubed and so it takes a few seconds for the oil to get onto the critical areas.