http://www.theguardian.com/football/2016/feb/24/mark-clattenburg-referee-catalyst4soccer Do professional ref have agents? And what does it mean by charity stuff?
I'm sure they are in demand for speaking engagements. I have seen referees, umpires, and the like as guest speakers at charity events in this country.
In Southampton alone, Jonathan Moss, Robert Madley, and Roger East (x2) have given talks since October (that I know of). I wouldn't be surprised if most of these guys are doing 2 events a week (at around £300-400 each).