Hope you get sorted, when i insured the first impreza and that was just a 1.5 it was 3.2k on a L license. I now have 2 years No claims and full license a while and +30 as well, paying 1078. got quoted 1672 on a STI Impreza, ask a bit into it with a good friend that works for an insurance company and was told the impreza fall into category 50 which means you can only insure NA if you are under 30. and its the general car categorization all insurance companies follow.
when that is said. I have to admit I do find it a bit strange you didnt research this before getting the car, as it is one of the hardest cars to insure. thats said I do of cause hope you get sorted,
as I suggested earlier why dont you buy a 200€ banger and put the scooby in your mums name and drive with open drive while you build up no claims on the banger. not like you have to drive just park it up somewhere and NCT it?