Actually, on further reflection, I find it easier to perform in front of larger audiences than smaller. When there are just a few faces that I can make eye contact with, I get nervous and lose my concentration. In front of a large sea of faces, I get a real buzz, and my concentration is increased. As a child I played in front of large crowds without nerves, but was terrified of the 'one on one' situation of Music Prac Exams, so may be that is why.