[hector0011]

Thank you O-Dog, I'll give a try and I'll let you know how it went. Thank you

The regular Cooper S and JCW actually run different models of ECU. It's not just a different flash, it's different hardware. You'll also need your ECU ISN number to match your CAS ISN for the immobilizer to allow engine starting.

That's not true. Depending on the production date regular Cooper S can have a EMS2 or the MS5150.
AFAIK the JCW models always had the EMS5150.

Like RocketSurgeon told you, the ISN number of the jcw DME as your CAS knows.

This is a R53. No CAS. These cars have a EWS

I have attached the JCW file and disabled the immo. This file should start the car if everything else is ok. So just plug in the JCW ecu and flash the file.
I've sent you the pass for the file by PM.
Please give feedback if it works like it should.