I would think in the S he has MMI 3 and in which case he may well thank you (and possibly me
Using VCDS enable the MMI Hidden Menu -
Adapation - 10
Channel 6 - "Read"
New value = 1
"Done, Go Back"
The next bit is done within the hidden menu which is accessed by -
Holding 'Car' and 'Setup' until the Hidden Menu appears. This can be tricky so get back to me if you struggle.
Using the joystick controller select 'Diagnose' and then 'Settings', followed by 'Tel Settings Misc'.
Change the setting to 'no WLAN/no NAD/BT/HFP'
Now he'll need to restart his MMI by -
Pressing 'Setup' the 'Scroll Wheel Button' and the top right function button all at the same time and then releasing.
He should now be able to enjoy his much cheaper than expected Bluetooth
If you have VCDS there are probably quite a few nice features we can sort him out with