Wondering why I had to top up the washer bottle so frequently a quick investigation revealed 2 dribbling headlight washers. I'm not sure what stops the water from running through the pump and out of the jets all of the time but I've read that replacing the tee piece that feeds each side with a Discovery item ( DCP 6656) which is some sort of non return valve, is a cheap fix. Maybe it puts a bit of resistance in the line which has to be overcome by the pump. Time will tell. The feed pipe is blanked off and fuse removed awaiting the arrival of DPC6656. For a tenner it's worth a punt.
Will report back.