Right now there's a housing crisis in Spain, with both rents and house prices through the roof. Many are blaming the excessive amount of accommodation dedicated to the more lucrative tourist rentals, so currently foreign investors are not particularly welcomed. Last week the government announced a new 100% increase in taxes for non-EU investors into real estate, we'll see if the law goes through.
For mortgages, it's tricky as you can't mortgage your UK house to pay another house elsewhere. And it would not make sense now that EUR rates are much lower than GBP. So you will need a lot of explaining and a good deposit in your chosen Spanish-located bank in order to get the loan. Also, in coastal places there are plenty of (expensive) consultants and lawyers that will do everything for you and the corresponding official translations, but in places like Salamanca you will likely have to do it yourself.
Salamanca is a big student city with loads of movement, so June whenever they are finished is a good time to check the market for owners willing to get out.
