2003 Vauxhall Vectra traction light is precursor to power steering failure

It seems in the cold or damp, and not always, the traction control light comes on. Sometimes it is ok and it does nothing else but when the car feels like it the ABS light also comes on as does the battery light and then the dials fail to work - (the fuel gauge and the rev counter) and disturbingly the power steering fails. The engine tone does not change and as long as you are on a straight road the journey can continue. I say straight road because she is very hard to steer without power steering unless you are only going 2 miles an hour. I have changed the battery for a new one and I have checked the alternator - which is charging ok. Any ideas?