Hi,
D8 cruise control is controlled by a d8 CC stalk, a master on/off switch, a CC control unit and the ECU. D9 cruise control is controlled with a d9 CC stalk (has on/off built onto it) in the ECU and BSI.
I have an early d9 and acquired all the bits for cruise control (stalk, master on/off switch, brake and clutch switches and control unit) and managed to get pug to activate it in the ECU for free. Problem is because mine is an early d9 it still has some but not all d8 wiring and there's no multi-plug for the control box
Hope this is of some help,
Sean