XFS Sportbrake discs

[Paulprior]

Just noticed that my front discs seem very worn, i havent taken the wheel off yet to check but inside and out feel that there is a lip of about 2mm, i assume thats too much, i have the Portfolio model, should i have sensors to tell me when they reach the limit?, does anyone know the disc and pad description?, if not do i need to ask jaguar and will they tell me that info.
Also the car has only done just over 50K., is this normal?

[w824gb3]

There is a pad wear sensor on the nearside front. Disks on the S are bigger than normal. 355mm instead of 326. Disks are consumables these days and at 50k your car is probably already on its 2nd set. If not they have lasted well.

[Paulprior]

So whats so different with pads and discs, i just replaced my BMW 5 series front discs after 100k, they were less worn than the jag ones after 2 sets in 53k, it seems very strange