Today was out with the old and in with the new. The old calorifier was in this empty space but this will now be underbed storage, the new calorifier is in the bottom of the wardrobe (with expansion bottle which was not in the old system). Tomorrow there will be a shelf fitted over. Several other modifications were made to the system - including 3 shut off valves placed in positions where they can be reached in an emergency.
I tried to keep out of the way for as long as possible, taking the dogs for a good run/swim in the excellent Spiceball Park and then walking back into Banbury to find some food and an optician, returning just in time to put my finger in the metaphorical dyke as he switched from the old system to the new - it felt as anxious as taking the patient off by-pass. That hurdle over, we held our breaths whilst we heated water by, first, the central heating and then the engine. No leaks - so far, so good.