I bought a replacement badge for my facelift R75 as the original was horribly faded and disintegrating. The replacement went the same way in a few weeks. I too then bought an older style badge, which apart from being more robust I think looks better. The new badge is still stick-on, but it is much thicker and showing no signs of fading so far.
I cocked up on the dimensions however, and it is smaller than the original (for a Rover 25 I think), but I fitted it anyway and it actually looks OK with about a 1 cm gap all round.
To get the old one off, I used a length of thin nylon cord (kite string) which I forced behind the top of the badge then pulled it left and right in a sawing action to cut downwards through the adhesive behind. A bit of rubbing with white spirit afterwards removed the remaining sticky bits.