Why are my Citroen Xsara's temperature warning light and 'STOP' light flashing at me?

Had a bit of a scare this weekend when my 2001 Citroen Xsara's red warning light above the temperature gauge and the 'STOP' signal on the dashboard started flashing at me. The thermometer shows nothing...

Where's my Vauxhall Astra's temperature gauge?

I have a 55-reg Vauxhall Astra Life diesel 1.7 CDTi. Where is the water temperature gauge?