To buy a property which you could directly resell should be the starting point. Let your broker also carry out your negotiations, the broker has no emotion during the negotiations and the buyer often shows that this is the house he is looking for!
Before making an offer, it is important that your finances are in order. You then directly can go for it and the buyer may just be accepting your offer faster than with someone who first has to apply for a mortgage or has to sell his house in the UK. Whether a mortgage is needed or not, have a valuation report drawn up by the Spanish bank, then you are sure that you can sell the property to someone who wants a mortgage.
Also, before making an offer let your broker first and foremost check whether the legally required papers of the property are available, by starting with the Nota Simple to request from the relevant agency, hence the broker will advise you further, what there may still have to be done to get everything registered in the escritura (purchase deed). All this can play an important role in the negotiations. If you come to an agreement with the seller and there are matters that still need to be arranged, please mention in the reservation contract “subject to …”.
Do not save on knowledge and security when buying a property in Spain! Go with an English-speaking broker who holds an office in Spain and speaks the Spanish language. A good broker can be the right intermediary for both the buyer and the seller!