I discovered a new discount supermarket this week, it is part of the Carrefour group and big in Spain apparently.
It is called Dia and has a pretty reasonable selection of both own brand and branded goods, and even some organic ones.
Website here where you can look up where the markets are, and also find the Ed discount markets. Not sure what they are like as I have not tried them yet.
I spent about 120eu today and have enough to feed the family for a week (main meals - turkey breast, turkey crown, roast beef, salmon, hamburgers, faux fillet) plus bread, ham, cheese, brioche, soup, eggs, pasta, sweets, toiletries and washing powder, fruit and veg etc. Some of that was own brand but most was branded goods. I reckon that I would have spent a lot more in a normal supermarket.
The sliced meats were a bit expensive in comparison to other supermarkets but the fresh meat was very reasonable.
Carrefour are also doing a basic range at very low prices.