Hope I am not breaking any rules here. First, declared interest, I work for Furniture Plus.
Second, I would advise anyone to do what you would do in England. Visit the shop, be it us or whoever, sit on the sofas, lay on the beds. 2 weeks on a bad mattress can ruin a holiday and if you are visiting regularly, can gradually put you off returning to your Holiday home. If you are renting, can prevent onward recommendation.
Third, make sure you get what you ordered, make notes or, better still, get a quote list of everything you select, take pictures if necessary, isn't that why phones have cameras.
Fourth, Bedsteads make it easier to keep clean, rather than divans, most shops sell both.
Prices. Make sure you know exactly what the cost is, it is easier if everything in the showroom is priced, like in England. Make sure the price is in Euros. It is a shock to be told the price of what you have fallen in love with is considerably more because the ad was actually in pounds.
Just some of the differences in buying furniture in Spain.
Hope this snippet is of help wherever you shop for furniture.