Dave,I suppose it could be peeled whilst sitting in the hot sun,but you would still have to initiate the peeling.
Remember though,I live in the west of Scotland.
We use a hot air gun,simply because you can concentrate the heat in a fanning motion as you pull the film from the glass,you just have to be careful not to overheat/melt any surrounding plastic/rubber trims etc,asbestos fingers help too!
