Are you going to use a french card, and choose a french billing, and ship adress in the UK? ofcourse it will raise flags and prompt 3ds because of it, also i heard french cards have the most advanced sec, so i wouldnt bother.
unless you are saying a UK card with uk billing and ship adres close to CH, then i wouldnt see a problem here, but i never done europe.
I believe in europe 3d prompts always if above $25, but some bins allow you to increase the maximum to like $300.
But i am unexperienced with europe.