Just seen this thread.
Let me know if there's anything I can do to help Carl, I'm just the other side of the bay, about an hour North of you.
I make no claims to be a 650 expert, only having had mine a few months, but willing to do what I can to help a fellow rider.
As for everything dying after a couple of seconds, Have you tried it on the center-stand, with a brake held,and hitting the starter as soon as you turn on to see if it will turn over?
If there's not enough juice to turn it over, could still point to a battery. If it turns over okay, it's probably something else killing things.
I can trek down with some jump leads, and an SUV big enough to make sure there's enough juice available.