Help me please

First of all anything I say here might not be completely accurate because I'm only 17 and am just going on what I think has happened - so it might not be 100% correct. I'm just trying to help my parents get their car sorted out (they work long hours during week and so I'm just doing this voluntarily). Basically we (my parents) bought a Nissan Qashqai from a licensed Nissan dealer 2 Saturdays ago (1.5 weeks ago). We had spent around a month looking for a car, took an interest in the qashqai and kept in contact with the salesman and waited until the car came in that fitted our requirements. We stated many times that my mum was going to use it to drive to school and back each day. We signed the deal 3 Saturdays ago and it was able to collect 2 Saturdays ago. The Qashqai we got is a £15000, 58 reg. Tekna, 2.0 diesel which had done 8000 miles (roughly) prior to purchase and was in perfect condition. We've had it since 1.5 weeks ago and we've started to notice a few problems - initially minor problem but now quite serious. As soon as we got back we noticed that the boot light didn't work, and we sent an email to the licensed Nissan dealer straight away, telling them of the problem. Then 3 days ago, the DPF (Diesel Particulate Filter) warning light came up on the dashboard. It said in the drivers manual that we should take it for a 20 minute trip at high speeds to clear it and the light should go off. We went for a 40 minute trip at 60mph but the light has stayed on and has not gone off since. The manual said if the light does not go off, we should not drive the car because it will make the problem worse and could damage the car. And so my mum has just had her Qashqai sitting on her drive and has not been able to drive it to school (where she works) and so surely we can get a refund for the car 'failing to function adequately'? Then yesterday, my mum just went to the boot to get her coat out the boot and the boot handle just snapped off in her hand! She didn't force it, she didn't do anything out of the ordinary, she just pressed the button, and tried raising the boot and the handle just came off in her hand!!! The handle is now just hanging by its electric cables and we can't do anything with the car because the plastic clips holding it on, snapped off when the handle came off!!! We naturally sent an email to the salesman alerting him of the problem, asking him what he will do to help us, like we have done after every problem we found with the car, but we havnt received an email response to any of our emails. My parents are just distraught because their dream car purchase (which I constantly persuaded them that they should buy) has now turned into a nightmare!! We can't drive it, my mum can't use it to get to work and so it feels like 15 grandmas just gone down the drain! What makes it worse is my dad works in Germany and so he can't help us and so my mum is really struggling to cope with her work demands and sorting out the car! I really think we should get a refund because the car was not sold to us as advertised (the boot light has never worked), and the car has 'failed to function adequately' (the DPF problem has prevented us from driving it, and the boot handle should not come off after only 1.5 weeks usage (although the car is second hand, it had a service by the dealer before we bought it and so no boot handle should be expected to last only 1.5 weeks!!). What can we do to get a refund for our nightmare Qashqai? Surely we can get a refund?! My parents never want to see the car ever again because it's just ruining their life at the moment and its making me heartbroken to see them this sad and depressed!