Beware!
He dealers that offer a week’s free insurance do so in order that they may tax the vehicle ready for collection. The cover provided is usually Third Party only.
If you have not been provided with this cover you should not drive the car unless your policy has a specific provision to cover these circumstances. The car will not appear on the Motor Insurers’ Database and if you are stopped the police may seize your new car. Even more important, if you have an accident you are unlikely to be covered.