How can I fix my Stoves gas Oven?

I have a Stoves gas oven - Newhome model number 059042012. The oven will light and the flame flares up as normal but it then doesn't die down when I turn the control knob down - so it's like the oven is on high all the time. I can get it to die down momentarily by turning the control knob right back to almost the 'off' position but within a few seconds the flame jumps back up again - resulting in burnt dinners! I am guessing the thermostat has failed but before I order a new one I wondered if anyone else had experienced this kind of problem with a gas oven? The hob burners are functioning normally.