Use a heat gun (carefully) or you old lady's hair dryer and warm them up.
Get under one edge with a knife blade and they should slowly peel off.
Don't rush it and you will get most of the adhesive off as well.
Wipe over whats left with some methylated spirits and Bob Sherunkle.
I like that one... saves me getting strange looks when I ask next door if I can borrow her hair dryer... thank youI pour hot water from the kettle on them first and then slowly dribble hot water on the sticker as I peel it off.