Try activating the headlamp wash button by holding it down and simlatenously turn the key in the ignition off to postion "O"- this should work...
It will be difficult to adjust whilst they spray unless u get someone to hold the headlamp washer activation button whilst you do the adjustments but that will use up a alot of the windscreen washer unless u wait for the level to get low and use water instead - if ur by urself then just place some tape on to the activation headlamp washer button and have the washer tank filled with plenty of water...
PS. On my car i never used to use the headlamp washer becasue that would only just make a mess on the headlmaps, bumper and bonnet...