Fucks sake. Never hire an "electrician". Use those TEA skills to do it yourself:
"Loose wire. Put it back on. Oven work! Ug!"Suspect! So I go a-poking and find this:
Fucking switch is burned and to fix it they just stuffed it on another pole. Now the thing doesn't work properly apart from on the small case of "oven get hot! Ug!"
You know a shit electrician when they have to go back to the car to get their DMM.
Zero service info available saying what the correct wiring is. Switch is 40 quid which is not end of world. FFFFFS