Ahh, I see some light at the end of the tunnel. Perhaps I had a leading comma there as a remnant when I changed my order of tags. I did try it with and without the trailing commas. I knew the metadata input fields forgave trailing commas and did have the thought that maybe this custom fields option did not - hence trying both.
It would be nice if it did ignore empty values thanks Charles. Then People wouldn't waste hours wrestling with an error they do not understand because it is "Programmers Speak". You do realise that there is quite a bit of this confusing teminology throughout the options, that makes perfect sense to programmers but is a foreign language to the rest of humanity? We need a bit of hand holding.
Thanks everyone for your help. Will try again tomorrow. Too late here tonight for me to avoid putting a brick through the monitor if things do not go to plan.
Dale