Leisure Zenith 55 Ignition fault?

When turning on the oven the self-ignition starts and continues firing long after the oven has lit, it continues firing intermittently for the duration of the cook/Bake, which may be 3.5-to4 hrs.
At other times the ignition will not fire at all when trying to light the grill/hob! (Using Push Button)
I have checked the push button for continuity and it is ok.
The Ignition worked before the clock had been set after turning the cooker back on.