I just have had the same problem, when i prized of the  red coloured insert in the tap head &  i was surprised to find no screw was no screw but there appeared to be a clip of some sort that lay on the top of the spindle
I simply pulled to the head  upwards to remove it 
mind you it took a wee bit of tugging to get it moving
changed the washer replaced the head job done
                
 superscot
                
 January 2011