The roof bars on my estate are starting to pit and mark. Does anyone know if they can be cleaned with anything. Also the chrome window trim is going in a similar way. Not had the car long so I don't know what the previous owner has done to cause this. Maybe used an unsuitable cleaning solution.

If they aren't too bad, you could try some autosol chrome plastic polish (not as abrasive as the autosol metal polish), and a microfibres cloth.

Is your car under three years old?

Yes it is. Don't think warranty will cover this just slight cosmetic issue

It should do unless there has been sign of stone chipping on the finished surface I would have thought. Either way it is not going to hurt to see your dealer.