The slump will be nothing to do with stamp duty, but increasing unemployment. Infact whether stamp duty is charged is almost irrelevant to house prices, its just more lost tax revenue for our totally clueless labour government.
People do not buy houses just because there is 1% off, Hopefully you can negotiate at least 10% off an asking price today quite easily, making the tax relief irrelevant.
I'm looking to buy too, but not untill the end of the year at the very soonest.