The film sold by sparkside is from hobbyking. So you can get it even cheaper if HK has it in stock but shipping might swing it in sparksides favour if you're only ordering a couple of rolls.
I've used HK covering for several years and like it very much. Unlike Phil, I think it is thinner than Profilm and a lot easier to work with around compound curves. I think profilm is possibly a little more stable and does not need re-shrinking as often.
For me, the real advantage is that you don't have to be so careful when you cut pieces from a 5m roll because there's plenty if you make a mistake. I'm sure we've all done it before where we cut a piece of profilm from their 2m rolls only to find that it doesn't fit because you've not given yourself enough of an overlap.
BTW, Tom Foster was/is a WMAC member.