First thing I did when I bought our old POP and now on our new TA was dump the space saver and stick a full size spare in the boot. Much better than any tyre repair kit (which we didn't get with our new car anyway) and I'd rather have a proper full size spare to put on if we get a puncture, than some awful skinny wheel, especially if you are out in the middle of nowhere.
Just lately, I'm seeing more and more people running around on space saving wheels because they are either too strapped for cash to go and buy a new tyre or they genuinely think they can get away with running around on these pathetic get you to a tyre shop wheels for weeks on end. The speed limit on these skinny space savers is about 50mph max or 80 kmph. I have regularly been overtaken on the M1 when I'm doing 70mph, by people clearly doing in excess of 80mph using space saver wheels.
I can't even begin to imagine the consequences of having to brake hard with one of these space saver wheels on, or hitting black ice with one on.