Do you have a black or a white disc? I assume black as it would be difficult to break the metal leg of the white ones?
Assuming you have the black disc that came with BT Plus and Complete Wi-Fi, I recommend you call the BT Plus helpdesk and ask for advice how to get a replacement. The number is 0800 800 150.
We don't advise opening products as there's usually very little you can do to repair and there could be risk of electrical shock if not done properly. Of course it's hard to advice specifically without seeing the product, but that's our general guideline.