valliant turbo max combi boiler problem?

Two problems.

I had a refit in my kitchen the controller for the boiler's wires got pulled out. What goes where?

To the controller, there are three cables - a mains, via the fuse switch. A cable from the boiler and one from the thermostat in the hall. I have put them in and there is power to the boiler and the controller but the thermostat light is not illuminated. I have hot water but no central heating.

Problem two.
An ongoing problem. Prior to the above and still happening. When I run the hot water for a couple of mins it runs cold. The temperature on the boiler drops dramatically. I turn off the tap. Leave it a couple of seconds then run it again. The boiler fires up. The water runs hot for a few seconds then cold again.