If you can do 'they've' as an abbreviation of they have, why can you not do would've as an abbreviation of would have? Or are those both things that would cause pedants much wailing and gnashing of teeth?
Erm. I think people have got confused. Would've is correct. That's why I said it. Excepted is not correct. That's why I mocked it. The Grocer's apostrophe would've made the signs even worse; I'm guessing that's why icklboo said it.