Does the Liberty-Flights UK site ship to Portugal? They sell inexpensive 100% VG flavors. Maybe you don't need to go to 100%, have you tried 50/50 or 70/30?
If you want to try it to see if it makes a difference in how you feel, you can go to a pharmacy and get pharma-grade vegetable glycerin and mix it with a little bit of distilled water. It won't have flavor or nicotine, but it is not unpleasant to vape it plain.
Mixing some VG from a pharmacy might be a good way to make the
e-liquid you have easier to vape.