Gas cooker oven lighting but not increasing surrounded by flame? i have a cannon gas cooker which have been immaculately ok until...

i have a cannon gas cooker which have been immaculately ok until yesterday,all the hob burners are burning fully and immaculately but the oven remains on low flame no matter what number i turn it up or down to,it is not an antiquated cooker so i don,t think age have anything to do with it,generally when i put oven on it burns low for about 30 sec and afterwards whooshes up fully,but it doesn,t seem to be doing that at the minute.in recent times cooking anything basic contained by it such as fish is taking about 2hrs,please,please give a hand,all sensible guidance very much appreciated as i disgust microwave cooking.
What is the bug on my porthole?
Answers:    To prevent a fight between Haza and Stitched up,the component is call a flame supervision device,probably a vapour pressure type.Its any broken or the bellow valve have stuck.Sometimes a couple of taps beside a spanner can sort it,if not,it requests to be replaced.Check the phial probe that sits across the burner hasn't moved out of position.
A corgi gas fitter is what you necessitate.
Where can i find..?
When's the last time you changed propane tank