I'm not sure if this related - historical version are stored online, arent they?
Anyways, dont think this worthy of a new thread so I'll chance posting here:
until recently I had the original SpiderOak software installed, from sometime in 2012 I think (sorry I didnt keep the version number).
This older version didnt prompt to update, so I didnt Short version of events
I discovered a ~27GB file in Users\Roaming:
Apparently this is resolved in more recent versions of their software, (which also prompt to update!)
I deleted the file manually after upgrading. Everything fine now...