You need to put the DVLA and your local police on notice of the problem. Once this occurs every case will be examined with an examination of the photographic evidence.
You should also endeavour to make a minor but visible change to your car which will show on camera as has been suggested elsewhere.
If any non-genuine fines come through inform them that you believe your car has been cloned and that you have previously reported it as such with as much detail as you can to support the case that it could not have been your vehicle.
DVLA will consider issuing you with a new VRM if the problem is persistent and cannot be otherwise resolved.