So from what I gather, in the UK you can have a section of your own insurance that stipulates you can drive a third party vehicle (ie. borrowed car) and be covered by insurance. You also need a valid drivers license and permission to borrow the car (obviously).
This feels very backwards to me. In Norway the car in insured, not the driver. For example I can borrow my friend my car, but if my friend crashes, I'll be liable for the insurance cost. If I want to borrow my car to someone under the age of 25 I need to have added insurance to cover the "higher risk" group. The reason we do it this way is *probably' simply because of tradition, but also the cost to insure is better calculated when you take into account the quality of the car, crash test results etc.
The car insurance is still valid if you lose your license, the car can still be driven by someone else and be covered by insurance, what matters is who drives.
The UK way seems like a huge hassle, requiring people who don't even own a car to have an insurance to simply borrow one.