We have R56 '05 MINI Xenon headlights - but the lights are mounted on the opposite side to the MINI so the headlight washers on on the outside, rather than inside, edge. Apparently this is deliberate, rather than *a feature, sir*.
Looking through Mini forums, it seems there's a switch inside the light housing:
"Get a little (metal) camping mirror and keep it in the storage above the glove box.
Use it to inspect the interior of the light housing. You are looking for something about the size and shape of a USB plug which has a sort of neutral coloured plastic shrouding.
It's fairly deep inside and those with hands like a bunch of bananas will struggle.
It doesn't click like a light switch, but offers resistance until a solenoid-like noise is heard."https://www.mini2.com/threads/bi-xenon-headlights-driving-abroad.161362/
This thread has a photo: https://www.mini2.com/threads/xenon-headlights.128330/
which looks like a real challenge to get to in an Aero!
Well I never: you learn something every day!