This really depends on individual circumstances. If you're insured with Policy Expert, you will be able to check if you are covered for this on your certificate of insurance. Remember that even if you are covered to drive other cars, this will be Third Party Only cover and only covers the Policyholder. Further details can be found in your car insurance policy book.
If driving other cars is not included within your policy at inception, this is not something that can be added on. If you still require driving other cars, please contact us and we can look at setting you up with an alternative insurance policy that includes this feature.