Right, I've got my Decathlon speed/cadence sensor fitted on my bike. It doesn't look as neat and tidy as the Garmin GSC-10 sensor, but for half the price I can deal with it. It looks like the second picture on
this page, so it has the two pieces with a wire in between, which doesn't look great, but whatever. It comes with four zip ties and two stretchy rubber things for fitting it to the chainstay. I opted for the stretchy rubber things, as I'd rather be able to take it on and off easily for cleaning, but the rubber things are a bit long for going round the relatively svelte chainstays on my Planet X bike, so I shimmed the sensors up a bit with some spare bar tap I had knocking around. They're not as secure as they would be with the zip ties, so I'll have to keep an eye on them. In any case, I've had to bend the speed sensor in quite a way towards the wheel to get the spoke magnet to register. I may be able to sort something out if I arrange the sensors a bit differently. Once I had the sensors in position I switched the Garmin on, went to the right bit of the settings menu and told it to look for the sensors and it found them immediately. I didn't even have to spin the pedals or anything to get it going. So, it's all good. I'll have to see how it plays tomorrow.