I haven't measured the distances, but if you are coming back from EIDW without stopping at EGPK then you might prefer to follow R14 and then G1. You would work Brize and Farnborough as you leave at CPT towards WOD. You would have to be up at FL110 until about 30 before BCN, however. If you can't manage that, London Info will provide FIS beneath and they or Cardfiff will arrange a joining clearance if required approaching BCN. Don't be tempted to try B39 during the week: the military play games out there and it is not available.