981 s Newbie /brakes/seatbelt rattle?

[Richard981S]

First Post so hello and nice to be here: (background: I have been driving a 2013 981 S PDK for 6 months and completely love it, was supposed to be a 3rd/weekend/dry weather only car but you can't get me out of it) 

 

I've got the juddery / lightening of brakes issue when slowing down over about 40 mph - is this likely to be ABS or discs/pads? My car is fortunately under an extended warranty but would like to go along to my OPC with just a little knowledge...

 

Also, I also have the thing where the passenger seat belt rattles both when connected (inside the clip, more of a clicking squeak) as well as when hanging open (definitely a rattle) - is there an insider tip on minimising that?

 

thanks in advance for any guidance.