Hot plate thermostat problem?

Hi, I have a stoves 61EHDO and am experiencing a problem with the temperature control.

It would seem obvious that thermostat has gone, however the problem is intermittent and I thought once the thermostat had gone it was gone totally?

We’ve found that if we turn the plate on by turning the control knob anti-clockwise to full heat, give it a blast of heat then turn it down to where we want it, it then controls the temp normally. If we turn it on from cold turning the dial clockwise, the plate never turns off, burns food and ruins pans. Only last week my halogen plate stared doing this as well (back right has been doing it for some months). It looks like the element, and thermostat are all part of one unit and as the halogen one alone is around £130, I’d like to be sure it is this that is at issue.

Is it possible there’s something else at fault, for instance the control knob or is there some other cut-off between the switch and the plate?

Any advice would be greatly appreciated.