@tp4sb 

The only way i can think to do this is via the alerts, try enabling the alerts for Client Authenticated with Portal (Wireless) that way any using the portal is logged / alerted

Personally never enabled it but in theory should work, email alerts will require you to have SMTP setup on the controller

  @Philbert 

Thanks... I will look into the portal part of your answer.

As regards the email: I set up the email with smtp and ran the test email succesfully when I first got the controller.  However, I've never had an email through since which is baffling.

  @tp4sb 

Oops.. I just re-read what you wrote.  I'll try to implement it later.  Thanks.

  @tp4sb 

I've now tried it but no email comes through. Oh well.. Hmm

  @tp4sb 

Just to say that the emails started working so I now get notifications through when new 'Guests' connect in my Outhouse.  

I've since also added the ER605 router too and despite it annoyingly wanting to change its subnet, I now have it configured and working.  (I had lots of trouble setting it back to the IP address that I wanted to keep, as per my old router, such that the devices I have with fixed LAN addresses on my network can continue with those same addresses).

A further problem now is that I now get random 'Large Ping Attack and dropped packets' emails all the time too.  I can't find a check box to untick to prevent these. Perhaps I might find the answer in another thread? 

Thanks