Germanshepherdsmum
I understand the point you are making about QCs commanding high fees, so there is no logical reason why Cox should not expect to be rewarded accordingly for his services.
But if, as alleged, he used his Parliamentary office and, presumably, Parliamentary time, then that is an issue.
I once worked as a 'temp' for a company in London and was caught filling out my agency time-sheet 10 minutes before the official lunch-break - I was reprimanded by the supervisor and told "you do not do your private work in the company's time". I was told to deduct 15 minutes from my hours worked. A bit petty, but the principle is sound - I was being paid to do a job, as is Cox... and we the taxpayers are paying him.
My (then) lowly status as a shorthand-typist / translator, compared to Cox's esteemed role as a QC should make no difference to the principle.