Managed to get the Guest LAN up and running for wired clients and all's working well. Users are sat behind a proxy and if I force the use of a appropriate wpad file I can get the WLC auth to happen and then push off to the proxy.
I'm trying to use option 252 in DHCP to present the WPAD url. Only issue that happens is that while the DHCP server on the egress interface is handing out addresses to clients on the ingress interface correctly, the WLC doesn't appear to be handing through the option 252 I have set in DHCP. I've used network monitor to see what the dhcp request process is dishing out in terms of options, and all look good if I'm not behind the WLC.
Anyone know if theres a limitation on the WLC that prevents DHCP options being passed through to the guest LAN?