There is currently no definition of 'cross-country' for licensing purposes in the UK. People will often quote figures such as 3nm or 6nm but the only published reference is in Section 1 of Part B of Schedule 7 to the Air Navigation Order 2009. This states that a cross country flight means any flight during the course of which the aircraft is more than 3nm from the aerodrome of departure. However, the definition relates specifically and only to Section 1 and, in fact, relates only to the privilege of a restricted FI.
Amendment 7 to JAR-FCL 1 introduces a definition of 'cross-country' as "A flight between a point of departure and a point of arrival following a pre –planned route using standard navigation procedures."The UK CAA, however, have not yet fully implemented Amendment 7 and so this definition does not currently apply in the UK.
Since the UK CAA has failed consistently to define the term, you are pretty much at liberty to place upon it whatever definition you wish and, should they not agree with your interpretation, it is up to the Authority to prove that what you have claimed is not, in fact, valid cross-country flying. Since the only definition, albeit not relevant to licence issue, is 3nm from the airfield, I would claim all of your local area and navigational flying as 'cross-country'. There are, of course, those that could, under this definition, claim 'cross-country' while in the circuit but its probably better not to open that particular discussion.