Is it possible for an 18 year old who has held a full UK drivers license to get insurance that covers them to drive somebody else's vehicle?

Hi,

I'm 18 and with Quinn insurance, this covers me to drive someone elses vehicle on a third party basis (I requested this over the phone so doubt if it is standard). However the premiums are very steep for this small privilege, my first year of insurance on my little 1.4L car was over £3,500. With 1 year's no claims it has gone down to £2000, but still comparaitively very expensive.

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