Should policyholder be registered owner?

As mentioned in the article on policyholder vs registered keeper, there are no laws which say that you need to be the registered keeper if you are the policyholder. However many insurers will refuse to provide a quote if the policyholder is not the registered keeper. If you do find a quote, it can be more expensive as well. In your situation, if the insurer has provided car insurance cover knowing that your uncle is not the registered keeper, then you don't have to worry about anything.  You have declared to the best of your knowledge the current circumstances and they (the car insurance company) were willing to provide cover based on these facts. So you don't have to change the registration certificate on his name or anything else.