fwiw, this old thread may have useful info about the precat O2 sensor in addition to what mike1967 has advised.
https://www.mini2.com/forum/second-...hange-pre-cat-o2-sensor-non-s-r56-cooper.html
https://www.mini2.com/forum/second-...hange-pre-cat-o2-sensor-non-s-r56-cooper.html