southern spain jan-feb

I have heard lots of UK pensioners do a deal over the winter and stay in otherwise empty hotels/resorts, i think there are even websites that organise it. ( i am not a pensioner) I am wondering how easy it is to a deal on the ground for 6 weeks? ie just turn up and ask around for a deal. Not worried about nightlife, a beach and a swimming pool will be enough and of course a few places to eat.
cheers
a