Sorry, delay in response. I ended up ditching Cura for a while due to an inability to get it recognising files. I can, however, get Cura 2.5 to work with no problems. Any version after that doesn't acknowledge that STL files exist!?!
I've attempted a reinstall of multiple versions with folder removal. No luck. The cura log is too long for my free pastebin.com account.
For example...
2.5 stl is an option!
Then 3.0 stl missing?