Depends what type of JCW
brakes they were!
I have the JCW
brake upgrade on my R53 JCW
which consists of monoblock calipers with a larger 294mm disc. I have only recently learnt this myself!
The later R56 models came with a 4pot Brembo upgrade but I don't know how much work it is to make those fit onto an R53 if that's what you are asking.