Somehow though, it's getting onto the fan, and spraying over the front of the engine and the adjacent cooling pipe. This narrows is down quite alot.
I reckon, the rad has split (common as muck) around the top coolant hose. Its then running down to the fan and getting flicked up while the engine is running.
If the rad has cracked, you probably wouldn't notice a leak until it had warmed up and under pressure.
I went to a meet once at bluewater, suprasurj did the whole 'lift the bonnet and look at my bling' that everyone does, he wasn't too happy when I pointed out the bubbles coming out of an invisible fracture in the top of his rad.
A good way of finding leaks is using a UV dye kit. You pour a little bit into your coolant, then run the engine, you then hold a UV lamp around the engine looking for glowing blobs of water.