Once the local search results are back, initial enquiries are received and your solicitor has dealt with any further outstanding issues, he/she will approve the draft contract.
Once the buyer has received the mortgage offer (if one is required), then contracts are ready to be signed and exchanged. The contract includes all the finer details. This is signed by both yourself and the purchaser with a completion date set. A deposit is usually paid at this point by the purchaser and held by the solicitor. Anything from 5% of the purchase price upwards.
The completion can take place as early as the same day, but is normally between 1 and 4 weeks after you exchange contracts. The balance is drawn down to the purchaser's solicitor, who will transfer the money to your solicitor. Only when this has arrived with your solicitor, can you release the keys to the new purchaser.