Solved! Go to Solution.
Are you plugging it directly into the DSL socket that the Openreach modem was plugged into?
This post should help.
One for user @licquorice
If more help is needed
Sorry, I got it working immediately after posting this.
For some reason the Quick Setup from the CD was not actually applying any of the settings for some reason. When I ran the Quick Setup from the router's interface it worked fine.