We are trying to sell at the moment, and we have lost the house we wanted to move to - someone was able to put a firm offer in, ours is still on the market.
the market is pretty flat at the moment, especially if you are selling a 2 / 3 bedroom property, so my advice is to get it on the market, so you have a fighting chance of getting a property you want when you find one.
I know this is the delicate balencing act - what happens if youo get a buyer and you haven't found anywhere, but if that happens to us, we will sell and rent, and then be ready to go when a property we want comes available.
Hope this helps.