Could someone ...

... please tell me if there is an easy way to get to the plug/plug cap on an '03 F650GS. Having dismantled half of the bike it is still elusive to those without 8" long fingers and a swivel in the wrist

Long screwdriver and the BMW plug key is all you need. Indeed it is faffy but gets the job done. I lever the cap off using the screwdriver, placing the plug key as the fulcrum. Then its a matter of patience and perseverance.