I take the above back. After the above crash, I tried to get this thing in the air again, but had an issue - the status led's flashed red really quickly ("there's a problem"), and it beeped incessantly. It wouldn't engage the motors at all, nor respond to the Tx in any way. I was -sure- it was a HW issue - maybe the GPS antenna in one of the legs had broken free? (apparently a common occurrence) or just one crash too many, and maybe the FC had given up the will to live!
I posted a vid of the issue online through the X380 FB page, and was advised to upgrade the firmware. I thought that was a daft idea - firmware doesn't break loose and fall out following a crash! What a crazy suggestion... But, what have I got to lose?
Sure enough, I loaded the new firmware, and now have a couple of 20+ min flights on this thing, no crazy flips, no crashes, and full green LED's (indicating strong GPS signal)
Back in love with this quad (so much so, that I'd better treat her to a new gimbal, and a new set of props...!)