From my RAF days many moons ago i remember Nimrods being based at St Mawgan in Cornwall and i think Lossiemouth or Leuchars in Scotland, so if nothing has changed i guess that it will be from one of those places, wher it was going i have no idea, i know that there are one or two BAe places in your part of the world, maybe its been into one of those for some kind of work doing to it.
Sorry i cant be more specific but there will probably be a more knowledgable reply than mine.
regards..Howard