I would expect to find, if such research was done, a smaller proportion of people with postgraduate qualifications. I suspect that the people incoming to red tops are coming from small news agencies, regional papers, websites, particularly specialising in gossip, celebrity gossip. They'll come from a variety of places and they may come from no form of previous journalistic activity or training at all.
Most journalism should take people in -- of whatever level of quality, should take in people who come from outside the normal streams because they will have special skills that are appropriate. It's very important to journalism that it does that actually occasionally. So I would expect the origins of people on the reporting staffs of red tops to be very mixed, probably.