Interestingly, despite having flown from Oklahoma to London with a number of stops, London to Prague, London to Malaga with a stop, London to Rome with a stop, etc. I don't have either a FAA or JAA CPL cross country, as I have never done those without someone else in the plane and they were all IFR.
The closest I managed was Fairoaks-Shoreham-Alderney-Fairoaks - alone, but IFR so no good for JAA and only 117 miles longest leg and only 249 miles overall, go good on that score either.