I suggest you ring the Broadband support line on the number found in My Account/Broadband & calls/Moving Home (even though you aren’t).
A URL always resolves to an IP address, so an IP address there ought to be acceptable.
Did you manage to fix your vpn issue ?
My work VPN doesn't work with now broadband often.
I turned off broadband buddy but I one I disconnect my work VPN if I need to reconnect to it I have to restart my router.
Did you manage to get a long term solution