Likewaise, Im glad I couldnt go on My Mums policy.
Mine in only £700 TPFT with 5 points (CD10), and 1 Yeard NCB.
If you spend enough time looking, you will get it below £1K, which is expensive, but as has been said, in 3 years when you wanna get / can afford a good car, your insurance is gonna be a joke, even if you are 21.
Get Pass Plus (all the big companies recognise it) and then go on your own.
However, be carefull with mods, a lot of the bigger companies dont like mods on people below 25.
Try HIC (dont charge for non-pwer affecting mods), they are quite competitive, number is on the main page on that big list.