Maybe you put a RJ45 on the end of the wire but termination was more of a 10base2 (50 ohm system) idea.

Now that you have all this wired you have to figure out where the trouble is.

DO NOT MAKE YOUR OWN CABLES. I find most folk can't get the wire pairs right.

So does the Cat 5 cable from the BT HomeHub to the loft work when plugged into a laptop?