It probably needs to be declared as a modification tuning kit.
Just declare the changes between a normal Cooper S to the JCW or check the dealer paperwork to see what got added.
https://www.pistonheads.com/gassing/topic.asp?h=0&f=164&t=759564
https://en.wikipedia.org/wiki/John_Cooper_Works
If you already have the number of years NCB then it should be transferable to any new insurance company, as along as you can proof it.
Any car modified insurance company should be able to sort this out easily enough for you.
Some car modified insurance company doesn't charge extra until power goes above 400bhp.
Just declare the changes between a normal Cooper S to the JCW or check the dealer paperwork to see what got added.
https://www.pistonheads.com/gassing/topic.asp?h=0&f=164&t=759564
https://en.wikipedia.org/wiki/John_Cooper_Works
If you already have the number of years NCB then it should be transferable to any new insurance company, as along as you can proof it.
Any car modified insurance company should be able to sort this out easily enough for you.
Some car modified insurance company doesn't charge extra until power goes above 400bhp.