Telefónica SA has received 300,000 pre-registrations to purchase the iPhone 3G in the United Kingdom and Spain, according to a CNNMoney report. A Telefónica spokesperson said customers have been reserving units of the iPhone 3G through the company’s website since it announced it would sell the device earlier this month. Telefónica is the parent company of O2, and operates under the Movistar brand in Spain. It will begin selling the iPhone…