Thirty-year-old cistern was looking pretty grim so it seemed worth undoing the whole thing, cleaning it up and starting from scratch. Various pros seem to like this kit and it’s very DIY friendly, so my toilet is now flushing beautifully. Unfortunately I didn’t understand that it’s designed so you no longer need an overflow pipe, and I bought (and trimmed) a new kit when just a cistern blanking nut would’ve been fine. I love the ingenuity of this design - so great that it adapts to different heights and that next time I need a new syphon I can change it without removing the entire cistern.