Given the speed limiter's weakness that it can't be permanently calibrated to true road speed, the alternative which I used on my Mk 3 Jazz was the speed alarm which gives a modest beep each time the vehicle accelerated through 30 mph (which can be adjusted). I found that to be useful because of the car's willingness to put on a few revs (CVT version) when pulling away from lights, roundabouts, etc and quickly exceed a 30 mph limit.