The UK (ANO 2005 as amdt) provides no interpretation for JAA licensing purposes. The definition standing in the latest edition of JAR-FCL 1 is irrelevant for UK-granted JAA licences and no distance requirement exists.
Under the US regulations the distance to which you are referring is (14 CFR 61.1(b)(3)) "at least a straight-line distance of more than 50 nautical miles".