I've had this car for three years and it's been good, but recently a slight coolant leak has developed. It seems to emerge when/after I've used the heater. Looks like it is coming from somewhere in the middle of the engine bay, but I haven't traced it to the source yet. I've been keeping the coolant topped up in the meantime.

What should I look for, and should I be concerned? The car cost very little, I don't want to put too much money into it.