Pause/Stop Lightroom Mobile from syncing

I have two work locations: Home and Photo Studio.  At home I have a good internet connection and wifi.  At the studio my wifi connection is via a 3G network (it's tethered via my phone), it is slow and expensive.

Here is what I am trying to achieve.  I need to have the iPad on online at the studio (for email and web browsing).  I  want to load my raw files in the Lightroom Mobile on the iPad at the studio so that I can check the images, do my picks, and do some basic editing.  However, LR Mobile insists on then sending the raw files up to the cloud, thus using up all my data allowance.  I only want LR Mobile to upload to the cloud when I am back at home on my reliable, non-metered wifi connection.

I've tried using the 'Sync only over wifi' option, but because the iPad is tethered to a phone - it THINKS it is connected via wifi when reality it is connected via 3G.

I think it used to be possible to sign out of LR Mobile and still use it without it syncing to the cloud, but now when I sign out, I can't get past the login screen.

Any suggestions as to how to work round this?