Now you're talking my language!
I agree completely that it's great to see the Spanish supermarkets broadening their beer selections. In fact not just Carrefour and Mercadona. I recently picked up a nice IPA at the 'new' Aldi (or is it Lidll) in Quesada. Even Mahou, the stalwarts of Spanish lager, are producing an IPA now which is acceptable (ie not my favourite), and available in Carrefour.
Talking about Carrefour, there is a small bar nearby, El Bosque, which used to sell a fabulous stout (7%) which was brewed in a small brewery in Elche,
https://business.facebook.com/cevique/. I'm not sure if the brewer is still going, but worth looking out for if you like a stout.