As a general rule, no legally binding agreement comes into existence until such time as a formal legal Contract has been signed.
As vendor’s solicitors we will furnish the purchaser with the contracts for sale and supporting documentation.  The purchaser’s solicitor will review these, raise whatever queries he/she considers necessary.  Once he/she is satisfied with the replies and that the other prerequisites are in place (satisfactory survey, loan approval etc) he/she will have his/her client sign the contract and arrange for the buyer to pay the balance of the deposit (usually to bring it up to 10% of the purchase price).  We will then ask you to sign the contracts at which stage they become legally binding on both parties. Usually until that point either party may withdraw.