Headlight washers. If you take your car onto European roads you are required to modify the headlight beam so that it doesn't tilt up into oncoming traffic. Halfords sell a universal stick-on beam converter to do this job and keep you legal, the Spanish are particularly keen that you have your lights modified. You can also buy the converter on the ferries.
It works well but the problem I found was that the headlight washer jet is so powerful it blasts wash-water under the self-adhesive converter patch and you quickly lose it. My remedy is to turn the headlights off momentarily when you need to use your windscreen washer. The headlight washer doesn't operate on sidelights.
