I have my car booked in to get a 30% tint on the rear windows only.  I am with Admiral and their options are Windows - rear darkened >30% or Windows - tinted <30%.
My question is, do I take the factory tint into consideration?  If so, then I would obviously need to choose the >30% darkened option.  I'm just wanting to keep myself right.

No. The % tint makes no difference.  If you want to keep yourself right then you must inform your insurer that you're altering your car from factory spec.

As I wasn't sure which level of tint option I should be choosing, I ended up getting in contact with Admiral via their web chat.  From the information I gave, they applied the Windows - tinted <30% option.

If you are in a similar situation, don't take this post as advice and always inquire with your insurer directly.

I think a lot depends on the insurer. When I got my Octavia 4 years ago I wanted to have window tints fitted and when I contacted my insurer at the time I was told they wouldn't accept it so I just left it at that. When my insurance was due for renewal I went with a different company and they agreed to insure with tints at no extra cost. I think I've changed insurers again since then and not had the tints knocked back as long as it's declared.

Hi.

If you have any issues with insurance at all for tinted windows then please feel free to drop me a line.

Regards,

Dan.