Asked the question, got a reply from SF as follows;
"I regret to advise that legally, we are unable to sell Gas Equipment marked with an orange Corgi shield to non Corgi registered plumbers. Please accept my apology for any inconvenience this may cause."
That was at 13:14.
At 15:30 another e-mail arrived from the same person at SF;
"Further to my earlier email. I can now confirm that the information in our current catalogue 94 is incorrect and you are able to purchase the Gas Equipment, however we do recommend that a corgi registered plumber fits the items. Please accept my apology for the inconvenience this has caused you."
So now we know...