Insurance "agreed value" for BMW E46 (316i Sport Compact 2000)

Hi All,

I am considering moving my E46 (316i Sport Compact 2000) insurance to an "agreed value" policy.

Can anyone advise me what range of values I should be considering / negotiating for "agreed value" ?

Can I increase the "agreed value", for example by paying a higher insurance premium? I am happy to pay a higher insurance premium.

How does "agreed value" relate to definition of "category C / D write off" ?

I originally paid £16,000 but that was more than thirteen years ago. She has done approx 150,000 miles. She is kept in a garage over night. She is (currently) and has always been insured full-comprehensive, but based on "market value" and not "agreed value".

Thank you for any advice,
Best regards,
James