Mel.
Let's inject a bit of common sense here. As you've changed your tow car you presumably don't need the old plate to be intact; it won't matter if you break it.
"Forcing" was probably the wrong word to use for the action of sliding a scraper up the back of the plate and gently working sideways to split the tape.If you were to cause any mild scratches with the scraper,those that won't polish out will be covered by the new plate!
Whilst splitting the tape with the scraper,you can gently prise the plate away from the panel - it's much quicker and lets face it,how complicated do you want to make it.
Halfords numberplate fixing pads are basically the same as cushion tape which you buy on a roll (with plenty left over for other jobs) but pads work out a lot dearer.
After a lifetime in the motor trade,mechanical and body repairs,you learn that there's an easy way to do things and a hard way.You just make your own choice.
Cheers Mel
Dave