Did you not ask the wardens why it takes so long? You’re not likely to find the answer otherwise. 

Had a fabulous few days on site.  If you feel energetic you can walk into Brighton along the sea front in half an hour.  Site staff professional  and helpful.  We arrived a day early but they still managed to accommodate us.   On the whole the amenities were very clean but on two occasions the shower cubicle had been left in an unpleasant state.  There was an offensive smell and a lot of body hair on the floor and in the drain.  I appreciate that the staff cannot constantly check the cubicles.  Perhaps a security entrance may deter non guests using them.  Having said that we had a wonderful time and will certainly visit again but next time I will use the motorhome shower.

,Denov Your post shows why some toilet blocks take longer to clean  as noted on a site we stayed on recently as follows "The toilet cleaning times are subject to what condition they are left in, as we clean to a standard which can mean not as per timetable"