Homark oven thermostat/control knob

Hi,

We have just moved and inherited a Homark oven, and by reading other posts I think Homark don’t exist any more (needless to say we don’t have an instruction manual). The oven is pretty old and a bit tatty but gets hot and cooks stuff, our problem is that the temperature doesn’t seem to be related to the marks on the knob. Sometimes we set it at 180ish and our oven thermometer reads 220, other times we’ll set it at 150 and it’ll read 150. It is a fan oven so I would expect it to be about 20 degress hotter than it’s set at. Can someone advise what the problem might be and whether we could buy and replace a part ourselves, or do you think it needs expert help?

Many thanks,

Susie