The best/cheapest card for Spain is Carrefour's
http://prepaid-wireless-internet-acc...in+-+carrefour


I've heard that also in France the supermarkets (Auchan, Carrefour, Leclerc etc) offer better value in terms of PAYG, and have longer "expiry dates" for less money, although I've no experience of them myself.
Here's one of them btw. http://www.leclercmobile.fr/