... a lawyer appears.
Haven't been invloved in insurance claims for years but the law doesn't really change.
First of all the termis have to go (temporarily). As someone has already pointed out if the insurance company can wriggle out of it they will. If they can say that you didn't disclose your modifications then the policy is voidable (on the grounds of your failure to disclose).
You can claim for your leathers, lid, out of pocket expenses etc. These are known as uninsured losses but you can claim from a driver if they can be proven to be at fault. Make sure you keep all receipts and proof of expenditure as the insurance company will want to see them.
Look into whether or not the police are considering prosecuting the driver. If they do, and do so successfully, then it has been proven beyond all reasonable doubt that the driver is at fault and you'll have no claim getting the drivers insurers to cough up the cash.
Don't accept the first offer of settlement (you can normally push them for more than they initially offer).
Most of all be thankful that you're alright and that you survived the off. Your health is irreplaceable, your bike is (love it though I'm sure you do) just a piece of metal, plastic and rubber which can be replaced.
If you have any specific queries please PM me as suggested (although I live a sad virtual life here most days anyway). I would have responded sooner but had a punter in the office with me.
Good luck mate.
Nik