Battery light comes on/speed'metr drops to zero on vectra 1.8 (2002 petrol)?

The battery light comes on in my Vauxhall Vectra 1.8 petrol 2002 after it is driven for over 5 minutes. In addition, the speedometer, temperature and fuel gauges drop to zero! I have taken it to vauxhall dealer who ran a diagnostic and after first look they were not sure what the problem was. After they look at it a 2nd time they said it could be the module and quoted £400 but couldn't guarantee this would fix the problem. My friend said it could be dodgy connectors behind the dashboard panel and to clean, tighten these.

Can anyone tell me if they have had similar problems and why the battery light comes on and all the dials drop to zero? Furthermore, my ABS light and airbag light comes on as well.