yitz: Yes if it is anything like the HG556a then you need to allow users to access from LAN/WAN side under Access Controls in the web interface.

I can't see anything along those lines in the web interface.

yitz: Do any of the combinations described in the support article give you access? http://help.vodafone.co.nz/app/answers/detail/a_id/24560/ 

Nope. It's a Spark supplied one, but I tried them anyway with no success.

If it's anything like the HG630, the password isn't the one that is user configured.  I thought I saw a blog post from someone in NZ that had decypted the firmware and found the password is something like the user configured one + an encyption string or something like that.   But when I tried finding it again a couple of months ago to get access to mine, I couldn't find it or figure it out.