The engine temperature sensor signal on green/blue coloured cable runs to pin 6 on ECU on both early and late versions of M3W. Common signal ground for this and several other sensors is on yellow/black cable running to pin 26 on ECU. So sensor is there and connected to ECU via engine wiring loom even on models without urban cooling kit fitted.
Have you checked through fitting instructions for urban cooling kit Neil assuming your car was pre 2014 model that didn't have it factory fitted, particularly the need to load new calibration file to ECU? Instructions are available for download
here as per previous thread.
