Hajo
We've same kind of problem here in Denmark.
I'm using Kerosene used for heating purposes, no fancy brand, just regular petroleum. I'm adding a "Diesel pest" additive, sold at boatshops. I ran into having alghea in the fuel and that is NO fun!
This additive is a part of Jet A-1, among other things.

I fly Merlin and JetCat.
Regards
Thomas