I keep seeing JCW Brake ducts for sale , but I don't see any difference between them and the ones on the S models .Is there any ?
What do you want them for? If it's looks, it really doesn't matter. If it's function, there are MUCH better aftermarket options.
Here in Yurp there is a bigger-engined diesel Mini, the SD. In the second generation cars, this came with the smaller Cooper brakes but with the working brake ducts of the S. It also came with serious brake fade if the performance and brakes were used seriously, so I'm doubtful that the brake ducts are much more than styling. Making my SD safe to drive fast has required conversion to S discs and aftermarket pads.
The oem brake ducts are not necessarily performance minded. There is a duct passage that continues through to the wheel liner but it is woefully small in cross section. The duct sort of points to the brake disc when the wheels are pointed straight ahead. I think it was done more as a way to be able to wash out debris that might clog up the oem duct at the bumper. If you want functional brake ducts you would need to adapt a kit that brings extra air directly to the discs. Most of our vendors supply this kit.... OEM Kit.... Really small duct... Aftermarket....
I think it depends on the year. I'd swear that the ducts on the exit side of my LCI MINIs were about 2" x 3". Unfortunately I didn't pay attention when changing my wheels today.