dont worry about how much you wrote, worry about what you wrote.
Markers would prefer to read short to the point answers rather than long massive ones that resemble a masters thesis.
English is impression marked, if a marker has to read through 8 pages of trollop to find one page worth decent material they arent going rate you all that highly. Remember that it isnt a test to how much in 2 hours, rather how well you can express your ideas in 2 hours.
DO not freak out if you felt you didnt write as much as the others.