They have a 30 day money back guarantee anyway. But I'm pretty sure once you get it on, you won't want to go back. Makes such a difference, you will be grinning every time you drive.
If you haven't already I would change the original DV before the remap. Go for a Forge 007p. And if you've got some money to spare I would also smooth the airbox and put a better panel filter in, and put in a silicon TIP. But it's not really necessary before stage 1. If you have loads of money to spare after the festive season, then get a uprated exhaust system too. It's on my list of things to do next, after I get some new tyres and save up again.