The campaign page mentions “European reseller” and “free worlwide shipping”.
I parse that as “within the Schengen area, no aditional cost/tax/custom fees should be expected”
For GB, it might depend on whether the phone is actually shipped in January or after Brexit…
Related: Librem 5 $599 reward - what-ifs, and import tax (UK)
(In contrast to above article, GB is shown as “cooperating” in the German Wikipedia article).