I know the KESSY key has a key inside but that only appears to fit the passenger airbag override keyswitch in the glove box. Is there a door that can be opened from the outside with this key?

I have looked to see if I can find a likely looking cover but so far it has eluded me.

Usually it's the drivers door. The cover to the left of the handle slides to the left to reveal the keyhole (it's a tight fit).

It's in the user manual!

Thanks all. I hadn't RTFM'd that page yet! In the UK MY2017 manual it is on Page 239 - not sure on other model years nor languages. 

Make sure you are pulling out the door handle when you are sliding off the plastic cover or you will struggle.