I've solved the mystery of my deflated tyre. It went down again, so I bought a new tube and stuck it in. I checked the old tube and it had a puncture, I'm not going mad after all. 
After 3 years of ebiking I've had 4 punctures. Only 1 was in the front wheel. Sod's law I guess.
After 3 years of ebiking I've had 4 punctures. Only 1 was in the front wheel. Sod's law I guess.