On an E36 they will be an additional kit that you fit to the current headlight units. Wire them to sidelights and they will be perfectly legal, as long as they aint blue i think.
Before applying, give all plastic a good scrub mate. I'll prob get slated for this, but a soft brush and washing up liquid, then a good rinse with very hot water.
If they are rings, they are an addition, so can be turned off, so will pass an MOT mate. Post some pics up of what you have seen and we will be better help. Gav
Imagine one one the wifes cotton pads she uses to take off her nail varnish. one tiny bit on this will do both sides of the foot step on the bus dude. You could do the whole trim on your car 2-3 times over with that bottle, and each application will last at least 8 months if done properly. So is that a big outlay for 24 months of new looking plastic?
http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_764457_langId_-1_categoryId_255233 It seems expensive until you have tried it. i'll post a full guide up to claying the weekend if your interested.
Clay.. its prob one of the best ways to decimate paint. Get an Auto Glym Clay kit from Halfords mate, feel the paint after clay, you will be amazed with the difference.