nyc
I can only summise from your post that the event was as follows. You turned right out of your drive, not noticing an oncoming motorcyclist who may have been speeding. The motorcyclist reacted moving onto the wrong side of the road and nearly crashing into you 20 yards down the road. The motorcyclist then preceeded to crash further down the road, which you did not notice because, you had driven on thinking there was no problem. The motorcyclist at a later date has found your car near your house and has taken details/pictures. They have then contacted the Police and their Insurers, hence this is why you have been contacted by the Police and the Insurers.
You will need to complete a claim form for your Insurance company explaining what you can remember of the incident. If you have any witness statements you should include these. If I were in your shoes I would make the case that you pulled out safely from the drive looking each way showing care to other road users. When you reached 20 yards down the road you remember having to avoid a motorcyclist who was speeding and on the wrong side of the road. In regard to the damage on your car this was existing and could not be related to being hit by a motorcycle at speed.
I personally believe that your Insurance company will find you at fault because from your information, I don't think you saw the motorcyle when you pulled out of the drive. Your Insurance company will therefore pay out any sums to the motorcyclist under your 3rd party cover and there is not much you can do about this. If you receive any correspondence relating from the 3rd party or their Insurers/legal people, just pass this to your Insurers, without any comment. Under the terms of your Insurance policy you are not allowed to get involved with 3rd parties.
The Police will not pursue you unless there is CCTV evidence to support a prosecution. This is now just an argument between you, your Insurers and the 3rd party/Insurers.
Huckster