So having part done the job I'd thought I'd add some extra info that may help others.
Firstly the FSU is located on the drivers side so the pedals create an extra challenge to access it. I also removed the panel that sits above the pedals, its impossible to access otherwise.
And Lastly the part I'd ordered because it is listed for the 2002 525 M was the wrong one. mine is 64118383835.