[lmm]

As a sibling post said, where are you getting your figures from? If they're correct, I'm tempted to apply the economists' argument: why aren't insurance companies doing this already? We see specialized companies (mostly just "imprints" of existing ones) for old people, women, track day enthusiasts etc. I could believe a plan to make say 10% ROI, but if this venture was as crazy profitable as you're suggesting I'd expect a "traditional" insurer to have done it already.

Bear in mind that your customers will choose the cheapest insurance: only those who are being charged more than #600 will apply. If that average of #2342 was actually 95% of them getting insurance for #300 and then 5% super-dangerous teens who're charged #40000 each, only the latter will take you up, and you'll pay out a lot on their claims.

All that said, I do hope you find a way to make it work. Insurance for under-25s is crazy expensive.