Simon B
If not current, I'd flash the firmware.

It can be done with the SM-BCR2 charger, but you will need an older version of the E-Tube software.
The latest version of E-Tube requires SM-PCE02 interface (it's an interface only, it does not charge)

Alternatively you can use the 11speed Bluetooth add-on. I done this several times without issue, BUT it is susceptible to interference and "can" brick your bike.
If bricked it can be recovered using the interface.

Barry