you'd need a S bottom end, rods and pistons, head gasket, intercooler and all the piping etc, Cooper S bonnet and probably a whole host of things i haven't listed.
also the battery would need relocating to the boot for the
JCW air filter to fit. you'd also need all the other thigns for the gearbox like starter motor, mounts, linkage, gearstick and so on. lots and lots to do, lots of money and insurance will be a bugger.