Superdan,
The no claims discount that you earn as a named driver is different from the one when you are the main driver (policyholder). I've talked about this before as there are two main clauses to this NCD which are as follows:
The named driver no claims bonus cannot be transferred to another company, therefore you will have to stay with the same insurance company to get discount on your next car insurance quote
The rate at which the discount is applied is not the same as that for the policyholder. If the main driver gets 10% off because of 1 year NCD, the named driver could earn maybe 5% (or more, but less than what the policyholder/main driver usually gets) for not making any claims under his insurance policy
I always recommend to take the plunge and take car insurance policy in your own name to start building no claims bonus earlier on but if the quote is too expensive, then you going for named driver where you can earn a discount with the same company is better than not getting any discounts at all in my opinion.