Hi Darren,
I didn't have any luck with the SessTimeout fix. As you said, its not exactly the same problem so thats probably the reason it didn't work.
At this stage I'm exploring alternatives. One viable solution would be to back up to the local drive and use robocopy (one of my favourite utilities 🙂 ) to copy the file to the network drive on a scheduled task. I'm going to do some tests with this after lunch.