I don't believe there is any sanding or treatment of the surrounding paintwork Matt. AFAIK you fill the chips with the colour-matched paint and then use a special solution to wipe off any excess paint which hasn't gone into the chip. I've seen before & after shots on various cars on different forums and the results all seem to be positive. I have no idea how long this lasts or whether the new paint shrinks, but it may be a solution for those who don't want a panel painted/selling a car(!). The front bumper of my GT is littered with stone chips, apparently it's very common, so I will give this a go when the weather's a bit warmer. For £50 it's got to be worth a try. I will, of course, do a full 'how to' guide!
Having looked at other forums, it's possible we could get a group discount if enough are ordered - anyone interested?