"I did not wire the plugs to the "B" specifaction, but to the BT colour code"
Any reason why you decided to wire it incorrectly?
But regardless of that, if you initially tried a new lead with (correctly) fitted plugs then it should have worked fine, you can check the cable by plugging both ends into the router and both link lights for the sockets should light up (it will also cause a loop in the network, so don't do it while you are using the router for anything)... If both link lights light up on the router but you don't get a link running from the router to the computer then it's a problem on the computers network card, possibly drivers, possibly a physical fault.