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When I enlarged it I found it was a lampshade but what is that coloured spaghetti at the back right?
Ahaa! That is the wiring! its a delicate setup
I've checked the wires too and from the 2 port valve (except the orange wire that goes nowhere, its all wired as is here "http://www.jturnbull.net/c_heating/sp_hw.htm") The timer goes directly to the boiler from what I can tell, presumably to the stat on the front panel, and then back to this box.
I'm worried that if I fitted a valve to the HW it might do something crazy like back up water from some overflow or something. I guess I would have to wire both the "micro switches" to the pump and boiler to prevent it pumping into closed valves (I assume its getting its power directly from the timer/via the stat at the moment).