Back when you mentioned this, mate. It sent me on another mission to see if i could find something cover this area, and i eventually stumbled upon these
wifi switches, which work with the "Tuya Smart" app. So i bought a couple and never got back to it until this morning..
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I also keep it predominately in the shed these days, and as it does, it becomes a PITA having to stand around 3-4 minutes waiting for it to heat up. So as of this morning i finally got this sorted and can now turn it on via the app, fuck around 'n go make a cuppa and enjoy that with a bowl or two once its heated up. Another bonus with the app, it's got an "Inching" function that allows you to set a nominated time to turn off, once it has been intially turned on. That way if i do forget, it'll turn off after 15mins that i currently have it set at, like yourself.
Admittedly, its cheap chinese electrical part though. What comes of it, i'd imagine i'll find out in time.