The ANO definition of cross-country as being any flight where the aircraft is more than 3 miles from the aerodrome of departure is contained in Schedule 8 of the Order and is preceded by the words "For the purposes of this schedule" (i.e. the definition is not valid in any other context). In the context of JAA licensing requirements, the only definition of cross-country is contained in Amendment 7 to JAR-FCL 1.001 and reads "A flight between a point of departure and a point of arrival following a pre–planned route using standard navigation procedures."
Since the UK has yet to implement Amendment 6 to JAR-FCL 1, let alone amendment 7, it is questionable whether this definition may yet be used but it surely will in due course.