Rick, I've tried tinting myself before and I'm just not patient enough. Besides I'm too anal to live with a crease or bubble hear or there. A cheap or homey tint job is an eye sore
Shop around and I bet you'll find a place that'll do the Mini for less than $200. It's a small car and the windows aren't complicated. A good shop will lay the film on the outside first to shape with a heat gun and trim.
I just had my BMW done, seven windows, for $210 with a life time warranty on the work and the film.
It'd taken me a whole day to do it myself and it would look ghetto as hell...so it was worth the $210.