I see from your later posts that you seem to have sorted it.
Yes, your drawing does make sense. You have a fairly conventional Y-Plan system - fully pumped with a 3-port mid-position valve to direct the boiler output to either the HW or CH circuit, or both at the same time depending on demand. If you study the Y-Plan wiring diagram at
The wiring has been done in a way which is all too common - using whatever cable is readily to hand rather than the proper stuff - so you've got the neutral wire of a T&E cable used for live, and the unshielded earth wire used for neutral! But hopefully you've now corrected that.
As I was saying in an earlier post, the neutral connection to the old stat was purely to act as a return for the accelerator heater (which gets slightly warm when the heating is on, and reduces the stat's hysteresis). Digital stats need no such fudge, and the neutral wire must *not* be connected to any of the switching contacts - otherwise in some condition or other it will get connected to live and cause a dead short.
As others have said, the base unit of the new stat needs an unswitched L & N feed from the left-hand end of your wiring centre, purely to power it - and your existing black and red wires (or their replacements if you've rewired that bit) must be connected to Common and Call for heat respectively.