Second hand car dealership recommendations please

Hi! 

In anticipation of moving to Spain permanently, I am looking to buy a fairly inexpensive runaround car. I'm going to be working from home so only really need it for occasional trips to Cartagena and Los Alcazares from El Algar. Looking for a left-hand drive automatic petrol car, obviously that is registered in Spain, and am looking at spending a maximum of 5,000€. Can I get recommendations on dealerships (ideally English speaking) in the nearby area that people have used, and if there have been any horror stories, can you also let me know about those too? If you know if the dealership will do a part exchange for a UK registered car too, that would be great! 

Thanks very much in advance. 

Tim