Phew, pump “correctly” fitted, cut down heat exchanger at the into pump end and pump inlet mating to it. An hour of pain saw the thing wrestled into place, clamps on, expansion bottle bolted on, auxiliary hoses on, ready to fill system. Horrible job, dreadful design, but, I suppose stripping it off and going back to raw water cooling and its associated lower output efficiency (I think) is at best questionable.