Go check your policy: Unless you have it as an extra, your own personal injury is not covered at all. If the claim is against the other party, then nothing in my policy has any affect on the claim I make on theirs. My car could be completely illegal (no MOT, tax or insurance) and I could have no licence, and yet if they drive into me I'm still completely able to claim any and all damages from their insurer. If I crash in my own car and break my leg, my injury is not covered by my motor insurance as standard. You cannot exclude liability for negligence which results in injury or death: This is enshrined in statute. Your insurer may let you pay extra for X amount of cover, but a basic policy does not. Although in fairness some insurers do offer a small amount of cover as an incentive to take a policy out with them, they certainly don't have to.
As I've said previously, I have disclosed to my insurer that I have a different wheel (well, I did on the MR2 and MX5 when I had them). They knew what I'd done exactly. I have no idea at all what risk they allow into their policies, how they front load them, what they will allow before becoming uncomfortable with the risk and refusing to insure etc. How could I? I don't work for them. Legally I only have to inform them of the material facts, which in this case would be that I have replaced X steering wheel with Y steering wheel. As to how that affects their risk and my policy, that's up to them.
I can understand a certain level of confusion about what a material fact is, but I can promise you that as long as you inform them of what you've done and do not lie, then that's fine.