Re: 166 Towbar
I had a Brink one fitted some years ago, only cost £170 or so. I used a firm local to me at the time, Edworthy's in Aylesbury. Did not need any bumper cutting from memory - the only slight gotcha was the rear lights on the car stopped working when the trailer was plugged in. Took it back to Edworthy's, and they sorted it easily.
It is probably worth mentioning that the 166 is a poor towcar really. The rear overhang is huge, and the rear shocks are not the strongest in the world. I towed my race bike on a trailer (probably 300kg all in) and it bottomed out fairly often on the rear bump stops.