To be fair RaisedOnBruce I don't think the mods know any more about the problems than the folk around here and I don't think there are any solutions without a software re-write. It's just a bad piece of software.
Update: I've tried creating a folder on my desktop, including some of the videos I wish to back up to the Cloud. The first video file happens to be nearly 7GB but won't sync (stops 80% of the way through), so that option is also out.
Is this a Mac issue, as I cannot believe I am the first person who wishes to store large files on the Cloud?
Using the Windows client I was able to upload, and download afterwards just to make sure, a 2.7GB MP4 file, that was the largest file I had available.
It was maxing out my 17Mbps upload bandwidth which is more than it can manage with photographs...
That was using, in Windows Explorer, right clicking on the file and selecting "copy to BT Cloud".
I've tried playing about with all permutations, on a Mac, on a PC, using drag and drop, using backup sync, etc and it seems that with a large file, it will transfer 90% of the way and cut out. It therefore seems that it is happy to go to 6.6gb of a 6.8gb file (and then fails), but on the other hand, it won't upload a 2gb file. It is as if it has an issue with completion. The largest file I have successfully uploaded so far is 1.95gb.