Well at least I know I had the code correct as its exactly what you have provided.
To answer your question the problem went away on the next run through, I had 5 errors all the same, changed 1 of them to see if it made a difference and then had 4 errors as you would expect.
It was 5 minutes later that the issue reappeared. I checked the code and it still had my change in it.
I wondered if it might be a cache issue but that's harder to check as the site is currently on a server that I don't have full access to. I guess the next step is to make the code change again (I reverted it) and then leave it for 24 hours and see if its still giving me the error in the logs.
Thank you for your help.