I gave this a try last weekend, and the difference is amazing!
The sandpaper is super effective, and it's remarkably easy. Here's my comparison shot:
Anyone else with a venerable car, you really need to give it a try - a badly crazed headlight looks bad, gives less light, and can be an MOT fail, so it's well worth the time. This way ought to be faster than toothpaste as well, since sandpaper is more aggressive and cheaper.