If you had to spray WD-40 into your cylinder to get it to kick over it may have seized. When you put the bike in a higher gear and roll the bike and let out the clutch will the engine turn over then. If it doesn't I would pull the cylinder and inspect the piston.
The US Vin for your bike started with 537-000101 and ended with 014044, don't know about UK. The bottom ends are much different from the YZ to the DT. Did you purchase new?