Anyway, the enhanced contrast on a sunny day is great. They make things pop and it's really pleasing to the eye. It’s made me think about filters and what they could do when shooting film.
Firstly Alan, it's not a stupid question, but very common among people who are not familiar with the use of filters in photography. Many decades ago I was fascinated by polarisers and wanted to see what they did. I made many atrocious mistakes (with slide film) before getting the hang of it. We all started like that!
Let's address your first discovery: what you see through polarised sunglasses, and the use of a polariser on the camera.
Using a polariser on your lens will produce much the same effect that you are witnessing through your sunnies (I too have a pair of expensive Bolle sunnies that are polairsed: they show me what a rainforest will look like under full polarisation without having to get the camera out!). The important difference though is that your camera can actually stuff up a good scene by over-zealous use of a polariser because the filter significantly reduces the amount of light reaching the film: too much and the scene will appear flat and dull. There is a right amount and a wrong amount, and how much you apply is governed to some extent by experience. What others have done is not an indication of what you should do, or what you will achieve. The best advice is to buy a roll of film, and a polariser, and go and experiment. You have already witnessed that colours 'pop' when you view them through your sunnies. Depending on the angle of view, colours will appear normal or stronger ("popping"). The same principle applies with the camera: as you move around with the polariser in place, the effect can be viewed in the viewfinder.
If your camera as on-board matrix/evaluative/3D or some other fancy-named metering system, you will require a
circular polariser -- a variation that is specifically designed to work with these advanced meters, and unfortunately this variety if often more expensive than the normal/usual polariser (
linear polariser). If you have an ordinary TTL meter, you can use
any polariser at all. Depending on the size of your lens, a polariser can cause quite a dent in the wallet: some can be around $27 or so for a 49mm polariser, rising (and rising, and rising) to more than $700 for German-made specialised polarisers (you keep these in the velvet-lined box with the family jewels...). You will not need (nor benefit from) the upper-crust offerings when starting out with experiments. That applies to just about every other filter too in the beginning.
There are many other filters, some doing little more to cut through UV haze e.g. light-pink Skylight 1B or near-colourless UV filters (these can be left in place to afford some protection to the front element in the event of a bang). These Skylight and UV filters often have different, confusing designations, with German manufacturers using something like KR1.5 for a filter that Japanese marque HOYA (made by Tokina) calls a Skylight 1B!
Warming filters (light to moderate brown in colour), colour correction filters (light to moderate blue) and then, for B&W, red, green, blue, yellow... all provide a specific effect of enhancing or reducing contrast and the appearance of tones. There is a bit of a learning curve!
Some people will cart around a vast armoury of filters of types and sizes. I get by economically, in black and white or colour (slide film), with
just one -- a polariser!
