Cannon Chester main gas oven not lighting properly

[Lemon cluster]

Hi All, please can someone help to identify where my fault might be...
We have a Cannon Chester (model 10458G). It's quite old and probably not worth spending much on. If it's a simple and inexpensive fix, I'll have a go..

The main oven is one that self ignites (just set the dial and it clicks/sparks away and ignites to a low flame. The sparker stops when lit. Then it turns up the gas after a delay of around 30 secs). At the moment, it lights the flame on low but never changes. If I blow the flame out, it will re-light immediately, so I'm thinking that the flame detection device is fine. I guess that it might be the thermostat, so the oven thinks it is already very hot and does not increase the gas.. something in there turns up the gas after a delay, so there is some control somewhere that might be faulty. Before I spend money on it, how can I eliminate some parts?

EDIT: I can see that the label on the cooker shows model 10548G, but there is no indication of MK1 / 2/ 3 etc...(seems to be spares for the MK3 only). Serial number any good?

Regards, David.

 

[Lemon cluster]

Just browsing for parts, I can see that the control for the main oven is expensive.. As it would be a "have-a-go" exercise, maybe a new cooker is what is needed.. my wife thinks so.... So no fix needed.