For those wondering what happened with this I finally worked up the courage to ring SKY tech support and go through the farce of sorting this out.
After 10 minutes of explaining that the userame and password I needed wasn't the one for accessing the SKY routers admin pages the guy on the other end basically told me they do not have those usernames and passwords on their system and that no-one does so it is impossible to obtain them, even if they did they would not support me if I used another non-SKY router (no matter how many times i told them I didn't need their support).
Eventually I got through to a manager who basically reiterated what the last person had said, trying to think out of the box I told them about the trouble I have been having with my sagem f@st router not allowing me to change the settings and that if I could be sent a replacement, only could the replacement be one of the older netgear routers that SKY use as I wasn't happy with the sagem (thinking I could crack that to get a username and password). This looked promising as I was put on hold whilst the manager went to see if this was possible, sadly it wasn't as they no longer send those out and don't have any in stock (which I didn't quite believe).
After a lot of farcing around they are going to send out a new Sagem F@st to me to replace the one I have as it genuinely doesn't allow me to change any settings, whilst going through the process of ordering one with the orginal person I spoke to he kept going on about how these routers are the top of the range and are really good and it was strange that I was having trouble with it, I had to cut him short in the end and go on a little rant basically explaining to him that their routers are most certainly NOT top of the range because it won't do what I want it to do!
Sadly I couldn't pull the "I want to cancel my contract card" as my parents wouldn't let me
So it looks like I'm just gunna have to wait until someone figures out how to crack this thing or try buy an old SKY netgear off ebay or something, either way I'm not a happy bunny and can't believe SKY get away with this.