Hi Simon,

I believe this issue has been resolved after you followed the advice from another user in this community.  Advice as follows and I'll close this question:

This issue might be caused by some temporary settings, that we need to reset. On the article below you will find the steps to do this. Try this with Studio closed.

Please try to do a repair installation according to the article below:
http://kb.sdl.com/#tab:homeTab:crumb:7:artId:6625

and

Goto C:\Users\[User Name]\AppData\Roaming\SDL, rename LanguageCloud.bin to LanguageCloud.bin_OLD. 

Re-open Studio and re-login to Language Cloud. "