Hi Mike and thanks for your comments,
Regarding the transfer of money,you are right, in Spain there is no system of bonded account, and the best way to do it is at the same time of the signing on the Notary, the seller gives you the keys, both sign the deeds and the buyer gives him a certified bank cheque (which is no normal cheque, because in this one the bank garantees that there are funds).
About the advice of not transfer any money before signature, I do not agree, in every purchase the buyer has to make a deposit(about 5% of the price)to reserve the house and the seller will not sell it to another that offers more, in that I think is different to UK, once you pay the deposit the offer is accepted. By submitting this deposit a contract is signed between seller and buyer (drafted and supervised by solicitors) in which all data are detailed of the property, the buyer and seller and the conditions of the sale. If the seller breaches the contract must return that amount plus another equal to the buyer. I can assure that this happens rarely, and more in the current economic situation, and if the contract is well written by a professional, the risks are minimal.
Mike is right, be patient and search without pressure, remember that the estate agent works for the seller, not for you.