Why does the site load so slow? [answered]
I found that when I applied my custom theme the page load ground to a halt - both on the front-end and dashboard. When I switched back to the default Elemental theme everything was perky again.
In case someone else has this same issue, I used this free tool -https://github.com/a3020/speed_analyzer/... - to identify what was the slow points within the page causing these problems. Interestingly the cause was remarkably simple - my theme had coded in paths to favicons which I had not created yet and C5 was throwing a 404 error for each of these, taking around 4 seconds per error - which was eventually causing the server to run out of memory. I also found that C5 was looking for a few theme files (strangely) in the "concrete" folder (I've got some more investigating to do on that) and once those dummy files were temporarily uploaded to the expected paths, everything was back to normal speeds.
Took a little while to work this out, so hopefully it saves a few gray hairs if you're in the same situation.