Drove to work all last week with no issues. Parked up Friday night and left it all weekend. Went to work early this morning. As soon as I turned the igntion the water level/coolant warning appeared on the dash with a beep.

Opened the bonnet and my coolant resevoir level was about 2cm below min.
Topped it up with some G12. Drove to work and back and seems ok so far.
Any advice on where to check for leaks? Not noticed any leaks under car yet. No idea if water pump has been changed in the past before i bought it (service history doesnt say so).
At 57K miles.