Loom is essentially hard wired into the fuse box, there is no way you can just unplug it I'm afraid. Best plan as stated already is to unbolt the fuse box and try to move it out of the way slightly so you can get access to your repair area. Depending how much space you need, if you feel you need to remove the whole thing it's a long process which I've personally done and it sounds like that's a non starter here.