I feel silly now, I was thinking two calipers! Just wondered what running two would do, if they'd be efficient. But I'm guessing with only one lever you'd only get the same amount of pressure, just spread over a wider area.
Thing is, my brakes are sh1te, I've tried everything and they're still sh1te, I have the right blocks for my rims, brakes are relatively decent, cables run smooth etc. they just don't want to bl@@dy well stop me.