Some of the major UK car insurance companies have recently announced plans to discontinue the third party cover to drive other cars. This service is normally provided to people with fully comprehensive policies, usually over the age of 25.
To put it simply, if you own a car and your insurance policy covers you to drive other cars third party - you should check with your insurance company whether the extra cover is still provided.
Due to soaring insurance costs a lot of young and old people are insuring cheap low insurance group cars and using the third party cover to drive much faster cars. This is most applicable to young drivers who, for example, insure a Fiesta and then drive their Dads BMW.
At the moment only some insurers have officially announced plans to discontinue the cover. However, it is likely the others will follow suit. It is worth checking when you renew or get an insurance quote what the insurer offers.