Campervan Sites in Northern Spain

Hi.  I'm planning my first road trip in my VW T6.  I'm looking at heading over to Brittany then down to Northern Spain and maybe follow the coast into Northern Portugal.  The problem I've got at the moment is finding sites in Spain.  There's an app that shows Aires, but these seem to be just places you can overnight, with no facilities at all.  Actual campsites, with toilets, water, showers, elsan disposla, etc. seem to be hard to find, whether using google or a couple of apps I've found, and whereas I don't mind a few nights without facilities I'd rather plan around campsites and use the Aires to fill in.   Given that overnighting by the side of the road isn't allowed - and not what I'm looking for - I don't want to go all that way to find it impossible to stay anywhere.  

I guess that my question is along the lines of is northern Spain as well equipped with sites as, say, France and Germany and I'm just struggling to find them or is it really the campervan desert my research makes it out to be?

Details - if it helps.  Planning to travel in April.  Northern Spain means sticking to within a few miles of the coast with maybe a trip into the Picos de Europa park for a few days' walking.

Thanks in advance for any help.