There has never been any distance requirement for a flight to qualify as a 'cross-country' under UK law. There used to be a popular misconception that flight more than 3 miles from the aerodrome defined a 'cross-country' but this was simply a mis-application of the authorisation privileges of an AFI. UK law requires that all flights in UK-registered aircraft are recorded in a personal flight log and the details that have to be recorded are listed in the ANO Art 228. The important thing to understand is that the flight log is personal and you may record in it any information in excess of the minimum requirements that you wish.