After having contacted the seller, they said it's something people often use in photography? I'm assuming it wouldn't be anywhere near as useful as an actual polarising filter - something which I do plan to buy once I can afford one as the 150x150mm ones are pricier than others - but would this work in any way for the mean time?
The polarizing filter mounts in front of the camera lens and should be optically flat. In other words, both surfaces should be parallel with the same thickness throughout. In many ways, an optically flat filter is more difficult to make than a simple lens. If not optically flat, it will degrade image quality. Luckily, most of the time, the distortions introduced are minuscule.
Most modern DSLR cameras use polarization as part of their built-in auto-focus and exposure metering systems. Because of this, a polarizing filter can interfere with these functions. Cameras that focus using contrast detection are not affected.
To avoid causing problems, there are circular polarizing filters, which are actually two filters sandwiched together. The first is a standard "linear" polarizing filter, which does the polarizing for us. The second filter, called a "retarder", scrambles the polarization so it won't interfere with the camera's autofocus and exposure metering.
I have never had any equipment harmed by a linear polarizing filter, and I doubt you will see any significant difference in image quality. Go for it. Then when your budget allows, get a circular polarizer to replace it.
Filters will stay flat better, last longer, and probably be of higher optical quality if they are made of glass, but they may be made of other materials and still function. I have used large sunglasses as a polarizing filter on compact cameras with varying levels of success, mainly dependent on the size of the sunglasses. (Obviously, an afterthought, something to try, just to see what happens, or could have happened had I been carrying filters around.)
That said, examine the item listing carefully. It appears to be a film, which may not have any rigidity on its own. If this is the case, you would need to apply it to another material, such as plastic or glass.