So far this rivnut tool has worked well - its pretty slow but gives good control over pulling the rivnuts. Needs greasing every now and then to make sure it slides, then the MO is to tighten, then loosen & tap the screw with a hammer to loosen, allowing the black mandrel to be easily removed:
Test pull of a pop rivet through one of the plastic P clips - no problem at all, didn't crack the clip, so all set now permanently fix the brake lines with them:
