Bare in mind I'm 20, and after a car for myself

My mum has an L reg fiesta (as some of you will know who read my first topic in here) I'm currently insursed on this as a 2nd driver, my mum being the named one. We pay ~£520 with Liverpool Victoria. Now I have a P reg car Lined up for myself. I thought insurance would be a pretty trivial matter as I ASSUMED my mum could change the policy over to cover the new P reg car of mine (for alittle extra) and take me off her car insurance which would reduce that payment by about 2/3s. Now as most of you are aware - which I wasn't - apparently my mum can't be the named driver of both cars?? Is that correct. Anyway basically, I'm after some adivce as to what to do now. Because my mum paid the insurance on the fiest upfront (full 12months) does that mean that money has been wasted?