Ok. Thanks.
I foolishly did not include the APs IP in the "allowed IPs" which bypass the captive portal. I did allow a whole range of IPs to bypass, which included the APs, but altered the range recently, excluding the AP in error.
For the proxy, I have now excluded private address spaces from being cached.
Now working, and now disabled, now I know it works :P
It's always so obvious!
Thanks for the help!