When switching on the oven in any setting the internal light comes on the fan comes on, in fan assisted setting, but no heat either top nor bottom or together or grill? The little red light on the switch does not come on either. All the gas hobs still work as does the clock.
take it apart, if the fan and light come on, an element shoult heat up when the red light is on. depending on which element you select.
isolate mains.
take it apart. (top cover - [be careful taking that off])
check the connections on the selector switch.