I thought I would update this thread to confirm it was indeed an original ARB I have with polo bushes fitted.
I just changed the drop links and put some new polo bushes on the ARB.
Interstingly I have plastic collars on the ARB but they are not under the bushes they are on the inside (towards the centre of the car) I guess in an attempt to stop the bar moving sideways?
Can't quite understand if they were the original plastic collars moved towards the centre or somehow some new plastic collars were fitted?
Knocking has gone which is the main thing - long may it continue!