Ant, I am following up a similar enquiry to you.
My understanding is that you may need to have an address in Spain (in the area where you want to reside/buy) so you might have to take a lease of a property until you buy. I have been in discussion with these consultants who may be able to advise with respect to your specific query. firstname.lastname@example.org.
Good luck – we don’t have much time on our hands and not helped by the pandemic!