I remember, in 2004, before we moved down to the south coast here in Sussex, we had an apartment/flat in Streatham, South London we needed to sell.....Once our tenants left we decorated and new carpets all round....Put it on the market on Monday, someone came to view it on Wednesday, exchanged Friday and they apparently moved in at the weekend.
Can be different depending on if chain involved, as PP mentions.....Gets a bit messy if chain breaks down.....happened before to us on other property.