Have you just recently bought the car from a dealer? The best way to get rid of a dealer sticker is to tell them that you are not willing to spend several thousands of pounds for the privilege of advertising their company, & to refuse to buy it if they leave it in. I even go as far as to insist they fit "anonymous" number plates.
One guy thought I was joking & left the sticker in place. You should have seen his face as I sat opposite him in the showroom on collection day, & phoned my insurance company to cancel the change of vehicle because I had changed my mind.