Peal it off & you are left (normally) with the sticky residue, clean that off with soapy water & a single edge blade with very light pressure or you can use a very fine wire wool. Washing up liquid in a spray bottle works best, forget harsh chemicals they are not needed
However if you remove rear window tint with demister elements, antennas, alarm tracks etc, it will remove some of the elements and may not work (they may be fine though depends on the quality of film and adhesive)
Thanks for the suggestions. Will be viewing a car with tints and just wondered how to remove them.
Phoned a window tinting guy and he quoted £90 for all windows. He did say that he couldn't guarantee not damaging the rear heated window elements. From what you are saying it sounds an easy enough job to do my self.