Graeme,
I don't know if we have the same problem mate but i did some investigation after finding a pool of water by the drivers front wheel like you, and it turns out that for me it was the main hose from the feeder tank that had come loose.
I must have not put it back correctly when refitting the bumper.
Here's the culprit...
I had to loosen the bumper and take out the headlight to get at it properly
And just to get on my nerves i now have to do it all again as the poxy thing shot off again after refitting everything last night
There must be a clip/clamp missing because when the headlight washers are activated(which is quite a strong blast of water)it's just coming apart.
I'll probably stick a jubilee clip or something on when i re do it tomorro.