Yeah, seems like somehow I've bypassed the switch.
Normally I'd have taken a photo of the wiring. But it looked simple enough, plus space was tight.
Indesit replied -
Unfortunately we are unable to provide any wiring diagrams, if you are stuck you can call our Chargeable Line on 08448...
Background -
Replaced a blown oven base element, which was tripping the fuse.
The oven was now on ALL the time.
Oven function switch at fault, two contacts had welded together.
Replaced that.
Now the oven will not stop heating up.
Have tried disconnecting the thermostat, but still...