Are you sure the alternator has a built-in regulator? In many modern cars the voltage is controlled by the engine management computer (by varying the field current, same as with built-in)
He didn't give the combi output, but they're usually around 30kW, enough to give reasonable HW flow, or what's the point? Unlikely that's the reason for the low flow.
Same here!
Why a surprise? The flow depends on the mains pressure and the height of the CWST. Sounds like the CWST is on the low side and can't be raised, so more often than not mains would be better. But it should have checked to make sure the change is worthwhile.
What made you change to a combi? There are pros and cons with a combi (mainly cons IMO), one problem being changing a gravity system to pressurised, as you've found. The installer should have pointed that out.
That's right, the solution is to throttle the hall rad more, so the roomstat there is less likely to be satisfied. The problem I see is when the outdoor weather is about 12° the roomstat will always be satisfied, so unless you turn it up you can't heat other rooms. Putting the roomstat somewhere...
Starmer talks as if we only need to increase defence spending because of pressure from the likes of Trump, and he's showing principled resistance by dragging his heels, saying 3% by 2035 or something.