I found the builders merchants out near you to be a bit of a nightmare, they just don't seem to stock much and it's not like the UK where if you go on to an industrial park you'll find a plumbers, electrical, timber merchants etc etc in one area, they are spread out all over the place unless I was looking in the wrong places?
The builders merchants in La Cala don't stock anything and about the best place I could find that had a selection of stuff is run by ex-pats which was AIM builders out near Marbella, past that I found myself using the DIY stores like AKI and Leroy Merlin, which has to be said are better than the likes of our B&Q, homebase etc.
Or maybe like I say I just didn't find them, knowing you're just up the road in Mijas (beatuiful little place BTW) where should I be using?