I wonder how much is just the sheer value of the car rather than insurers considering them to be particularly risky?
While stating your argument you left this as the last one, as if it is the least significant one. In reality it is the most significant one and you should lead with it, otherwise you run the risk of sounding disingenuous.
>license for more than 9 years [...] when I was 19 and had just passed my test my insurance was £1200p.a.
I assume you did not adjust the £1200 value for 2019 according to inflation, GBP purchasing power, et cetera. Nine years is quite a long time for price changes. Have you tried getting a quote for a "sporty car" in the current year?
Ireland (so utterly dysfunctional insurance market) but as a person in my mid-30's with impeccable driving record but no NCB (hadn't owned a car for years) I pay ~€1550 for the cheapest possible insurance on a 10 year old Honda Jazz. It should be under half that with a year of no claims.