That's completely contrary to my experiences when attending QT in Coventry last December. Everyone I spoke to had applied via phone or online for seats and then by luck had been picked.
Applause and jeering came from all areas of the crowd which was an extremely wide cross-section of students, public and private sector workers, a few retired individuals and people of all backgrounds and race. I was also extremely heartened that despite Coventry being a labour heartland an effort was obviously made by the producers to keep the audience as diverse as possible.
There was a small area (30 seats max) to the side of the stage where people who seemed to be party affiliated were sat but they were explicitely asked by David Dimbleby to be silent through the filming process because audience reaction is about 'public opinion, not political volume.'