P Reg Citroen Xantia SX not starting, unknown indicator flashing?

Citroen Xantia SX indicator flashing - what is it indicating?

Our P reg Citroen Xantia SX will not start, it does not turn over. The furthest right top indicator which looks like an inverted empty bottle or a degraded F is flashing yellow. I've checked the oil - OK and filled up the water, the battery is OK and cannot find where the brake fluid is in the engine.

Please advise how I can get our car started.
Thanks for looking and I hope you can help.