Any ideas how to correct these marks on our bonnet? Can only see them when in sunlight.
I think you need a paint expert/body shop to cast an eye over it.
From the pics it looks like the lacquer coat is failing or something has been on the bonnet like a cat, they sometimes like a warm bonnet to rest on, who knows? The pattern of the paint damage doesn’t suggest it’s scratch marks though 
Looks like an issue with the lacquer coat to me, possibly caused by sun exposure. Seen this before, if it happens it usually occurs some considerable time (years) after the affected panels have been resprayed.
Oh dear! My first thought was “don’t take it out in the sun then” 
Seriously though, it does look bad. A few options are,
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Have the bonnet resprayed
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Purchase a good used bonnet in same colour (only four nuts/bolts to undo.
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Have the bonnet vinyl wrapped in a contrasting colour
My previous NC, I know, it’s red but you get the idea 
Barrie