Your best bet is to phone around a few schools who already do training on DA42s - that way you'll go somewhere that's already set up to operate your type of aircraft, so you won't spent any of the course working out flight profiles. Most would have no problem with you providing the aircraft and paying a fair hourly rate for the FI/IRI! It normally takes a bit of paperwork to get the aircraft approved for CPL/IR instruction at an FTO, but far from impossible. Just allow a little extra if you want to test on your own aircraft, like the flying time to get it to a staff examiner for approval for test and expense of putting CAA examiners on your aircraft.