I understand what you are saying , but the worst case scenario is that the pump fails to run when the boiler is being called for and the boiler cannot get rid of its heat at all and the heat exchanger splits and floods your house. As i said before it is the responsibility of the installer to...
You shouldn't need to know where the wires go, that is up to the installer if he has not wired the boiler correctly he has not upheld his part of the deal, give him money and he installs you a boiler as per manufactures instructions.
The central heating pump has probably seized try undoing the silver screw in the middle of the big round bit on the pump on the left hand side of the appliance and spinning the center of the pump (beware as water will come out of here and could be HOT). If this doesn't work and you have power to...
This problem sounds as though it is a plate heat exchanger or blending valve problem if you were in a hard water area this would point to a scale problem. As you are in Staffs. I would probably look at sludge being the cause or that the thermal store is not getting up to temp. Bite the bullet...