Hi Romain,
Thanks for the reply! The twitter:site attribution was correct, however, twitter:creator was blank. I have now changed twitter:creator to @elcaminob too. Do you think that this is what could have been causing the problems? It is hard to tell immediately as I only experienced the problem occasionally. Is there some kind of re-crawl facility I need to use for this change to take effect?
Thanks for your help,
Tom