yep sticky pads are the way to go... unless you want to get one off!
Best thing gow down to do it all and buy yourself a Stanly mini-stanly knife it has a 4" exstendable snap-off blade, winde the blad out then just slide it up the back of the plate. if you want to be real carful then put some masking tape over the tip to stop it digging into your paint work.
Thats what ive done, but then if your old plate is the same reg as your new one, IE your private plate before you had it respaced then just sticky the new one over the top, and you wont ever notice, that way if the pigs pull you over tell them you fitted your "show" plate for a meet the other day but havent been able to get the damn sticky pads off!!!! works for me and saves me a £60 spot fine for ilegal plates...