Lots of places sell the sensor but I found only one place on the internet that had it with the exact same end on it that I could just plugin without having to work out which of the (tiny) three pins go where and make up a new connection.   I chatted to the owner of the shop via email, who seemed to reply within minutes each time, and he was happy for me to send it back if it did not fit.

While everywhere was covered in snow for the day, it was clear (although not warm!) under cover where I am able to just about squeeze my bike up on the stand.    I fitted the new chain within minutes, it now has a quick link which will make it easier to remove in the future – it should last a year and 4000 miles or so.

For the sensor I quickly unplugged the old one and plugged in the new to give it a go.  Not only did it fit, but when I turned the pedals the LED lit up and the rear wheel started spinning on its own.  Bingo.     It was a fit fiddly getting the old one off and the new one on.  The new one had miles of cable which I wrapped around the frame a number of times, I put on a spot of sealant with the hope to stop the water getting in so easily.   Upon taking the old sensor off I was able to see how the rubber at the bottom had come away from the rest of it, which explains why it stopped working after all the rain.   I’ll take it to pieces at some point and fix/throw away.

I’ve been riding off of the ‘sticky’ throttle for three or four months and have been getting quite used to it, but it’s not the safest approach.   I will get a surprise in the morning when I peddle off and the motor kicks in!