Why not have you boyfriend insure it on a classic policy and you be a named driver, not totally honest but may do for six month till your 21.
Make it a classic car policy when you do as the price will be sooooo low, ok you'll earn no NCD but when you save ££££££ who needs the no claims. plus in a couple of years when you go to a normal policy (if you do), you'll be older with more experience and no accidents so will get decent prices anyway and can build them up then.
Either way, you'll pay out ££££ being so young with such little experience on an RS turbo, but then it's worth it