Its probably the bottom corner of your radiator perishing.
I spotted the same leak coming from mine. I took it to my local friendly ex VW mechanic and we spotted it straight away when it was up on the ramp. Apparently mine won't be the first he replaces!
We spotted this back in September and I put some Wynns Radiator Stop Leak in as I was really skint at the time. Believe it or not the rad is still sealed to this day, I was expecting 1 month tops!