Have tried some friends trolleys in the past with mixed success, and seen countless trolley failures over the years at festivals.
We now use our Thule Chariot with the jogging wheel at the front. It collapses/disassembles well, has a large capacity, takes a reasonable weight of stuff, and can get through most mud or rough terrain without issues.
Although, if there is due to be a trolley man hiring out the sturdy ones for £10, I would use these. They are usually very robust and designed for the sort of purpose that you want it for.
Also with using Trolley Man there is no chance of someone nicking your own fancy trolley from your tent to get stuff to their car on the last night of the festival.