Sarah,
If you already have car insurance in your own name, then you are most certainly allowed to drive your aunty's car with her permission. You need to look for the words "can drive another car with the owner’s permission" on your policy. This should give you third party cover which will allow you to drive her car over the weekend.
If you've never been registered for car insurance or if you cannot find the words stated above, that's when things become difficult. Since you're 18 and all
short term policies require that you are 21 or over, you will not be able to get
temporary cover. The shortest insurance cover you can get is for 1 month and that's with
eCar Pay As You Go Insurance. This type of insurance is available for a month and can be renewed or cancelled on a monthly basis.
