Peugeot 107 single beep?

Hi,

I have an 09 Peugeot 107 manual, 1 litre. After filling up this morning, I drove about 100m away and my car beeped, just once. The same beep you get if you only have one bar of petrol. I didn't think anything of it but driving home from work (about 30 miles, motorway driving) I heard the beep again, just one single beep. There are no warning lights on the dashboard, nothing else seems to be strange.

I've read that constant beeping can mean a problem with the clutch, but it's just a single beep so I aren't sure.

I drive around 45 miles a day. I've had it for about 8 months and nothing has gone wrong yet (that I can tell at least)

Can anyone shed any light on what this might be?

Thanks!