I have a Baxi Maxflow Combi WM with a dial room thermostat attached. It all started when the house was baking hot earlier on this afternoon. The rads were all hot, but turning the room thermostat down didn't make any difference. I turned the selector switch to hot water only but the rads still heated up. The pressure guage was at 2 ish, I've now turned off all the TRV's and it's gone back to 0.5. If I turn one back up again, that rad heats up. The hot water indicator neon is on constantly, and now the hot taps are running cold! The boiler's making a low hum sound. The burner light's not on, and the central heating light doesn't seem to come on at all! Any ideas? Thank in advance.