Hi Ian, I'm also 21 and am currently insuring a 350z in my own name, all modifications declared (quite a few of them!) for £2,600 fully comp. I've got no NCB and have been driving since I was 17 so I'm sure you can get a better quote than 4k! Have you tried adding your Mum onto your policy in your own name, so that she is just a named driver? That also helps to get it down I think.