The fix for this was to configure the SSL VPN cia CLI. This enables the Https://(external ip) distribute the Anyconnect VPN. To connect an SPA525G to the system via VPN, you will need to enter the static IP manually into the phone which then proceeds to authenticate with the UC500 router. THe VPN Phone Wizard won't recognise the SSL VPN, so this cannot be done in CCA.
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