All the Spanish sites I've stopped on have same blue/white socket as uk campsites but I would take a 2pin mains socket adaptor as you do in France. Polarity is not an issue with modern electrics, on any continental site you can have different polarity on same multi ehu post so I wouldn't worry about it.
Location: west country Joined: 29/3/2009
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I too have only ever seen the standard blue/white uk euro socket in Spain. I am not aware of reversed polarity in Spain and in my experience there are few examples in France. I would always travel with a 2 pin continental adaptor and a reverse polarity adaptor.
Not being a qualified electrician I an not in a position to advise on the rights & wrongs of reverse polarity but you will find a number of lengthy and sometimes heated threads on the subject.