The first thing to remember is that many of us have taken out Type 1 and insulin and Libre on many flights with no issues.
The second thing to remember is that insulin is fine at room temperature for a month.
And the third thing to remember is that, unless you plan to leave your insulin in the window of a car without air conditioning , it will not get too hot.
I have flown many times and travelled to places hotter than Spain (last time I was in Dubai where it was 40 degrees at midnight) and never had any issues. I take Frio but only to use when I am outside. For example, when hiking and camping in India where there was no sign of a fridge for days. My Frio wallets are now 18 years old and still perfectly fine for travel. So definitely a great investment for Type 1.
When I say I have flown many times, I mean, literally hundreds of times and never contacted the airline beforehand. Since I started using self check in, I have not told anyone at the airline. The only reason I can think to tell them is if you feel you need extra hand luggage for medical purposes.
And I only tell airport security if they explicitly ask because I consider it personal information they do not need to know. They have never questioned my Libre and I have never had a problem with the Libre after going through a body scanner or the x-ray. I carry a letter from my diabetes clinic but only needed to show it once in 20 years. Some people also carry a copy of their prescription.
I always take twice as much as I need of everything. This includes back up meter and test strips plus a battery for my meter even though I have a CGM.
Diabetes should not cause any trouble when travelling but, if you are anxious, you can wear a sunflower lanyard.
When in Spain, make sure you have plenty of hypo treatment with you as most of us find the change in daily regime can affect our BG.
Some people use the fridge in their hotel to store spare insulin. I do not trust most hotel fridges and, provided you keep your insulin away from the heat, it does not need to go in a fridge.