The nokia kit probably uses an amplified speaker in the footwell. There is no mute kit evident in the boot.

Unfortunately the TCU install will not be easy.

For the install on your year of car, the BM24 you have will not support the TEL_NF audio input, I am lead to understand. Instead it has dual voice coil front speakers.

You may need a telephone retrofit harness. If you intend to make one, you will need to find a way of passing the telephone audio either to the Nokia speaker, the dual voice coil speakers (if fitted), or buy a BM54 and the 17 to 40 pin adaptor.

You may find the vehicle has the four black speaker wires for the dual voice coil speakers in the harness at the connector X400/X3221.

You will also want to make sure your TCU works. Early GSM models do not, despite the Bluetooth sticker. See Stringback's recent TCU thread in this forum.