Spain - which mobile network?

[GeorgeAL]

I plan to holiday in spain and use a Sky data SIM to do some work while there. Which Spanish network does Sky partner with? I need to check signal coverage at the location.

[maurelius1]

Same here, I could use some info please 

[WillcoxFamily]

As Sky run on O2 whidh is owned by spanish conglomorate Telefonica,  that is probably the best one to use but will make no difference to your UK allowance in EU