Option 1 states that the North Atlantic Co-operation Council (NACC) is the new organization which replaced the North Atlantic Treaty Organization (NATO). This is incorrect. NATO has not been replaced by NACC. NATO still exists and continues to serve as a political and military alliance of North American and European countries.

Option 2 is that the United States and the United Kingdom became members of NATO when it was formed in 1949. That is correct. These two countries were indeed founding members of NATO, along with ten other North American and Western European nations.

Option 3 suggests that both statements 1 and 2 are correct, but since statement 1 is incorrect, option 3 is also incorrect.

Option 4 suggests that neither statement 1 nor statement 2 is correct. Since statement 2 is correct, option 4 is incorrect.

Hence, the correct answer is option 2, indicating that the United States and the United Kingdom became members of NATO when it was formed in 1949.