well bt homes hubs are shite, the last few i have tinkered with where shite to setup basically, everything is about as clear as a dirty window lol. Anyway, i do know that the bt homehubs are not configured for remote access (remote admin for router) afaik this is for all homehubs, but it was alteast for the ones i was tinkering with a while ago, they just donot support it. there are tutorials for forwarding ports on these things but even i struggled on this and believe me, i have worked on many many many routers big and small.
you could try
Port Forwarding Guides Listed by Manufacturer and Model - PortForward.com for some direction and as always google is your friend.
incidently, you do not have to use the DDNS service on the router you could use the one on your cameras webgui (it should have an option for this) if you use dyndns.org (the most widely supported dns service) when the camera detects a change of IP it will update dns records accordingly just like it would on the router.
you would have to port forward and open the ports on the HUB (you will have to excuse me i dont often work on this so am not fluent in them) or check to see if the bt hubs have a DMZ option (de-militarized zone) and place the cameras IP into this, however the DMZ will leave all ports open to a particular IP address so make sure you set good strong passwords for all services on the camera, i.e. FTP / HTTP / TELNET etc etc , but it is only a cctv camera so nothing too major.
hope this helps.
p.s. despite what BT says or anyone else, home hubs are shite. BT`s stance on remote admin was `we dont allow it on the home hub as it is a significant security risk` lol, this coming from a company which carried on relying on MAC based WEP keys many many years after WEP was deemed near useless lol.