A UPS is a battery back up system. I personally advise anyone using a desktop pc to get one.
What they do is plug between the electrical appliance and the socket, similar to how a multi plug extension lead works.
But they have two advantages. One being surge protection being built into a lot of them. This stops power spikes blow the hell out of the circuitry and secondly they have the batter back up. You loose power and the battery kicks in, giving you time with a computer to shut it down or with a tv receiver, plenty of time to reset the power.
I believe the computer shop in Dolores sell them. The one on the Dolores, Catral road. If not the big electrical shop in Elche, which is in the same shopping area as Carrefour has a very good selection of them near the computers. With Carrefour on your right in the carpark, great big shop directly in front of you.
The only deciding factor then is how much you want to spend. In theory, the more you spend, the bigger the battery and the longer it will last.
Quick add on to this
Just looked on the media Market website, typical Spain, they list them but show no prices.
Media Markt®
After a few minutes of flash screens and god knows what, you get to a screen of many items. Top right, you see a search box, enter UPS into that and in the five or six pages of results there are a few listed.