<<FL33>
That's about 3,300 feet. Did you mean that Dawdler?
<<I've turned up a page that says that aircraft shouldn't enter a volume 5 nautical miles (9km) horizontally and 1000 feet (300m) vertically around another.>>
Not the full story. Separation between two aircraft depends on various factors and can range from 10 miles/2000 feet right down to a few hundred yards and no vertical separation. In busy airspace it is usually 3 miles horizontally or 1000 feet vertically but on the approach to an airport if pilots see other traffic ATC can instruct them to provide their own separation which may be considerably less than that mentioned above.