the mobile rates for all providers have been changed in all EU countries from July making them more accountable for what they charge for country to country connection within the EU, and therefore improving tariffs a bit.
I have spent a lot of time travelling the EU for work, driving trucks, and what we used to do was keep a mobile that only priveledged people knew, such as the work office, and our normal mobile would be turned off at Dover to stop any Tom Dick or Harry attempting to call, and being tempted to answer.
Being that people are asking what happens in Spain, as they only travel there, i would still turn off my UK mobile, but when in Spain buy the cheapest Spanish Mobile and pay as you go Sim on a spanish provider.
I would then only give this number to my son/daughter/mother/father, or other trusted confidante............this would reduce your incoming call load, and if you need to phone out, also your call charge there too, as you wont be using your UK mobile in a foreign roaming agreement.
Hope this helps, used to save us a fortune!
P.S, dont forget to change back to the UK phone when you get back to the UK!!