See, this paragraph says otherwise:
If I were an awkward insurance company having a bad day, this is how 'minor' these things are:
Two seats - they're the things keeping you safe and secure in the car. Cheap or badly fitted seats aren't ideal in any situation.
Steering wheel - if it falls off...
Oil cooler - could easily be a fire risk, not to mention the fact that in an accident you could lose your engine if it's damaged and you'd expect to claim for it.
I'm not trying to be an idiot here, and you've clearly learnt a lesson from the situation, but it always pays to show why these things are important to insurance companies. Hopefully at least one member sees this and decides to declare everything rather than nothing