Matter's not how many times you tell, or explain to any house buyer, UK or Spain, do not give a deposit over to any Estate agent, say this until blue in the face, still people will do it, because the friendly estate agent, and they are your friend, because they want you to buy from them, could, and can, talk many into doing it this way.
Give your deposit to your solicitor and tell the solicitor to inform the estate agent, 'Deposit received' simple as that.
We still hear of people that have handed over fair amounts of money, usually over the internet, to gain access to 'You have just wont the Canadian lottery,' many of these people are not dope's, even though they know full well they never entered this lottery, so if some still do this, what chance do others have face to face with a dodgy estate agent.
Not at all saying all Estate Agents are this way.