Gotta be careful with a hairdryer though as it can heat the paint up a bit too much and make it bubble.
I used hot soapy water, give the badges a soak, the gently eased them off using an old credit card. You have to be really careful though incase you scratch the paintwork so I suppose dental floss would be a miles better idea. The glue will come off with a bit of rubbing with your fingers when it's dry. Then clean any residue off. It's all fairly straight forward in all honesty.