Well that depends on what you mean by "set up the freesat cable". Do you already have a dish that was once installed for Sky? If so, then simply plug the existing cable into the back of your PZ81.
If, however, you don't have a dish at all then you need a dish installed and that could cost anything from £80 upwards depending on the complexity of the installation. Often, the shop you bought the set from would have offered an installation (unless you bought it on line, of course).
Don't fixate on the £80 though; that's for the simplest and quickest of jobs. If you want anything fancy done or the dish needs to go on a chimney, then expect a bigger bill. Just make sure you find a good installer.