If you have a standard cavity wall and a long enough pilot drill you could come in from both sides (no euph) in order to make a nice clean cut in both internal and external walls.
i.e. drill pilot hole through both walls from one side, then pop outside, affix core drill, drill, pop inside, drill, done and time for tea.
If you have a standard cavity wall and a long enough pilot drill you could come in from both sides (no euph) in order to make a nice clean cut in both internal and external walls.
i.e. drill pilot hole through both walls from one side, then pop outside, affix core drill, drill, pop inside, drill, done and time for tea.