I´ve just received the new Winter Camping brochure with 25 sites advertising cheap long-term winter stays. The brochure states stays from 6.99 Euros a night for 3 months including two adults, pitch, caravan, car, water, electricity and 8% VAT.
Scanning the sites in the brochure the cheapest I could find is 8€ a day including the above plus wifi and paid in advance. This is at Sierrecillo in inland Malaga province near Antequera.
A fairly new site flatish site on the edge of a protected natural area which is good for walking. Being inland in won´t have the same mild temperatures as the coast but makes a great base for exploring inland Andalucia and is about 50km from the Malaga coast.
The Winter Camping brochure can be seen here Winter Campings Andalucia
Read my newer post Over winter in Spain - Long stays