[Engine] Top mounting

[Fred Brook]

Hello

I am in the process of changing all the engine mounts on my 2006 1.9d.
I have done the bottom rear and the gearbox ones but not the top one. The reason being is that I'm not sure how to get the actual mount itself off - the bracket is easy enough to remove. Is there a tool or some obvious way that I am missing ?
Also,  does anyone know where can I get a replacement centre nut for the top bracket.

Thanks 

Fred