I found the problem - it was because at some point I decided to put in a mailserver into the the advanced section of primary features - not sure why LOL - I think it may have been an earlier attempt to fix the non-emailing of several of the components.
As a result all mail was going to addresses on the server, but not to anything external - the script was not even attempting to send them - it wasn't as if they were hitting the mail queue or anything.
Anyway as far as I can tell the problem is solved - thanks for everyone's help. I have tested as widely as I can - and at last I know have new members registering.....
