The problem is that insurance companies use the same term (NCB) for both policyholders and name drivers. In the past, only policy holders would get the no claims bonus and if you were a named driver, you wouldn't get anything. Nowadays insurers are rewarding named drivers if they haven't claimed on their policies. However the NCB for named drivers is not necesarily equivalent to that of a policyholder. If a policyholder received 10% discount for a year's no claims, there's no guarantee that a named driver will receive the same discount (most likely he would earn less).
And to answer your second question, NCB given to a named driver cannot be transferred to another insurer. So you will only get the discount if you were a named driver with, say, company A and did not have any fault accidents, and you are looking to get an insurance policy from company A but in your own name now, that is, as a policyholder.
Hope that clarifies things for you now.