OK Daft Question alert.....

It's a model J - Caliper (somehow) fits to the mounting brackets which bolt to the fork leg. I've noticed the caliper has a little bit of lateral play .... this normal (rear caliper also tilts side to side a bit)

Cheers.....

Looks like it's worn/loose slider pins - Manual suggests cleaning and refitting with loctite (just incase anyone was wondering)