Ok ARB bushes are different to Auxiliary dampers/Bump stops.
Anti Roll Bar bushes (ARB) hold the ARB in place. Bumpstops sit on pistons of the shcocks.
Sorry to update jacked up the car the other day, and pulled the aux dampers downon piston. Cleaned the top surace of them and also the underside of the suspension mount where they touch. Applied liberal amount of GT86 to the surface that touches the underside of the mount and the damper rubber. The noise hasnt dissappeared but has reduced by about 90%. Quick fix which should make them last a bit longer.
The underside was full of corrosion / oxidiation of the aluminum which could explain noice etc.
F30 335i M Sport