Disc Brakes *Completely* Ineffective Over recent months my front and rear disc brakes (Hy Rd TRP on my Genesis Croix de Fer) have become increasingly useless, to the extent that I now have to cycle very slowly because it takes at least 5 seconds to stop, regardless of speed, with full pressure on brake. 

I won't take you through everything I've done to try and counteract this, but what I did yesterday (without touching it with my oily oily hands) was:


remove wheels
use degreaser on rotors and entire brake area
use sandpaper (quite fine grind) on rotors
change brake pads
tighten brakes and centrally align


and... they're ineffective as ever. 

Things I haven't ever done are: bleed brakes (they're hydraulic at bottom and mech at the top), or look at/remove brake cable.

Things I didn't do yesterday: bed in new pads, use isopropryl alcohol rather than degreaser (generic muc off spray).

There hasn't been even a slight improvement in brake power, is it that I didn't get any contaminants off the pads? Didn't bed them in? or something more mechanical that I need to get checked out?
I've had my fair share of hydraulic brake woes this year so I'll list the things I'd check - I am aware that you've done some already. Firstly some questions though:


Are these brakes using mineral oil or dot fluid? If it's dot fluid, when attempting to bleed the system you may want to take extra care and de-gas the liquid like with Avid brakes.
The comments suggest cable actuated hydraulic brakes, this is a new one on me for bikes so I'll assume that the cable has been checked and is moving freely / not rusted.


Things to try:


If you've cleaned the rotors and pads lately then you might need to go through a decent bed-in procedure to transfer some braking material to the disc rotor.
Bleed the brakes (if you need the Avid kit to do it, buy the pro kit, the other one is awful).
Sand the pads.
Check that both the pistons are moving freely in the calliper.
Degrease the whole area - isopropyl alcohol (IPA) will clean most of the muck. Use paper towel or new rag rather than an old greasy rag.
See if you can get some life back in the pads by heating them with a gas flame from either a blowtorch or gas ring on the hob for 30 seconds (be careful, use pliers to hold the pads). See if you get flames or lots of smoke which indicate contaminants.
Try new pads, swap to another brand or compound. Sintered is good for wet, grit and mud. Organic has better initial bite but not as good in the sloppy conditions.
Check the hose and connection points (banjo bolt &amp; bleed nut) for leaks.
Check around the pistons for bubbles that indicate a leak.
Look for areas around the calliper where dust and grit has stuck to any oily residue that could have come from a leak.
Take the rotor off the hub and give it a good clean in the sink with degreaser, washing up liquid and finish off with IPA.
Take some pictures and video of the calliper so we can see if there's anything that more eyes can pick up.
Enlist the help of your local bike shop - show them some (financial) love and build up a good relationship with your local mechanic(s).


Make sure that your isopropyl alcohol is as pure as possible so as to make sure it doesn't leave its own residue.

Try a few more things and report back soon.