Where the driver is the owner of the vehicle, he may at the time of electing that the test shall be deferred specify a period of seven days within which the deferred test is to take place, being a period falling within the next thirty days, disregarding any day on which the vehicle is outside Great Britain, and may at that time require that the deferred test shall take place on premises then specified by him where the test can conveniently be carried out or that it shall take place in such area in England or Wales, being a county borough or county district or the administrative county of London, or such area in Scotland, being a county or burgh, as he may specify at the said time.