There are no hard and fast rules about what is or isn't a classic car. While the rolling 40 year exemption for MoT and tax is a good starting point some cars get there sooner (TVR, MG) often because of low production volumes or an historic badge on the nose, while some take a while. In fact, some new cars can be insured on a classic policy. We'd put the Mazda 121 in a similar category to the Nissan Sunny - there aren't many of them left, but there doesn't seem to be a huge amount of people who are interested in them either. Of course, if you're interested in a 121 there's great news for you as you'll have the market to yourself and a car that stands out from the crowd. If a car means something to you, then of course you should cherish it - regardless of age.