It now appears to fine... however, there is one difference with how I did it. I used a different USB stick. With the previous one, I get the skin error, with the new stick, no errors with the Confluence skin at all. I tried the previous USB stick and no-go, tried the new one straight after and all good. Just to be sure, I reformatted both sticks and copied the same image and recreated the problem or got the skin working repeatedly...
