Have you tried getting quotes without the mods? If it's a decent amount less it might be worth removing them and selling them, offsetting some of the insurance cost.
Also try adding an older driver to the policy. Just adding your Mother to the policy (not that I'm saying she's old - just an example) as a named driver can lower your premium by almost half in some cases, and just cos she's on the policy it doesn't mean you have to give her a set of keys. Try it out on Moneysupermarket.
Also juggling your occupation can help. Obviously tell the truth, but most peoples jobs are not in a set catagory and can fit in a few. If this is the case for you, try them out and it could help lower your premium.