Tony,
If there are no air leaks then I dont see why you can't get them bled through, unless your method is wrong somehow, I'm going to write how I would do it, please don't be offended if this is what you are already doing!
Undo bleed nipple half a turn, pull in brake lever, keep it held in while fluid/air squirts out, keep it held in and tighten the bleed nipple...repeat until just fluid squirts out with no air...
Can you confirm thats your method? If not give it a go, if it is your method, then I think you have another issue, but I dont think it will be because the disc rotor is worn, that would just need a bit more fluid in the system to compensate