I don't care whether they're 'average Joes' or MPs (or school teachers). 4 weeks 'sick' is taking the piss.
The CONTRACTED hours of work are irrelevent, having been accepted and agreed to by both sides before the employment was taken up. If the public don't like it, then complain to those in a position to change the status quo...otherwise it's just sour grapes, or envy based upon ignorance.
For a lot of my working life I have worked about 15 hours a week, with virtually zero days off due to sickness , and no pay if nothing produced. A self-employed Consultant.
When I was in the Civil Service, it was accepted that you took the maximum number of 'permitted' paid sick days. Seems that little has changed, except perhaps the sickness 'allowance'.