The confusion over driving licences is in part linked to the general confusion over residency. There seems to be a refusal by some to accept that if you move to and live full time in a foreign country, you can no longer be resident in the UK as well; it's one or the other. Of course, if you are a tourist, i.e. not resident in Spain, then your UK licence, so long as it is current and valid under the terms of the issuing authority (DVLA) is perfectly acceptable. But if you are a resident of Spain, you are a resident of Spain and nowhere else.
Perhaps looking at the reverse situation would help. If I move to the UK permanently, I can continue to drive on my Spanish licence as long as it complies with the same conditions as if it had been issued in the UK. That means I can use it "provided it remains valid", and for 3 years or until I'm 70 (whichever is the longest). Since Spanish licences only have a validity of 10 years up to age 45 and 5 years from 45 to 70, at some point I am obviously going to have to "renew" my licence for a UK one. I could return to Spain to renew it, using a flase address (i.e. one at which I am not resident) but that doesn't make much sense. Of course, I could exchange my Spanish licence for a UK one as soon as I want to, which is exactly what I would do. I have no particular emotional attachment to my Spanish licence, and I know that having a UK licence in the event of getting stopped by the police in the UK, will avoid any possible confusion.