My licence change over was handled by Miguel Angel Palacios Rey, insurance agent, of Av. Marques de Rozalejo 1, Los Alcazares. More details on Google. He arranged a medical in San Javier which included an eye sight test, questions on any medication, having a photo taken, a fairly wide ranging discussion with a doctor who spoke english and a session in front of a screen where, using two knobs, I had to keep two lines representing cars on two " roads " which weaved from side to side, in simple tandem at first but later weaving independently . I found this easier to do by sitting back from the screen rather than getting too close to it and quite enjoyed doing it . I think the fee was around €30.
Make copies of your U.K. driving documents for future reference.