What international telephone code is00447?

As dialled from abroad, 011 44 7xxx xxxxxx or 00 44 7xxx xxxxxx would indicate it's a mobile (cell) phone number.

01447 xxxxxx as an area code was "Kingston Communications Premium Rate" in the late 1990s and it's to be assumed those moved to an 090x xxx xxxx number in the Big Number Change in 2000.