If you are involved in an accident with an uninsured rider or driver you should take their details, vehicle registration and model and contact the police immediately. This may effect your insurance cpmpanies ability to pay out. Sometimes this involves legal fees to bring this situation to a conclusion.
Normall you cannot build up any No Claims Bonus by being a named rider on someone else's policy. However there are car insurance polices where this now may be possible. Check to see if these benefits are yet to be applied to the motorcyle insurance market.
You can reduce payments by offering a voluntary excess, but keep in mind not to offer a huge sum as you will need to meet it if you make a claim. this also means it may no be worth claiming for a small accident, or repair. Some insurers still insist you inform them of all accidents, even if you do not claim.