The temperature oopf my jaguar x type from 2003 2.0 diesel will not rise to normal parameters no mater for how long i drive the neadle goes up and down but not remains in the middle allways low

 

get a hand held non-contact temp unit,harbor freight tools, then you will see what your engine temps actually are. test it in different areas of engine.

may be the gage or something simple,diesels have a tendency to run cool when running under a light load.

 

+1 but also read with OBD. Compare and see which is wrong then fix - post again with temperature readings if you want more ideas.