The UK election commission recommends pencils as there was a worry that ink could become invisible in the ballot box if there was an organised effort to replace the pens. But that’s the provided writing implement. I don’t think there is any rule for bringing your own. And I don’t think the counters have time to invalidate a vote because of marking type.

Are those exports tariffed?

You can be nice and signal that you don’t want to be AI scraped. There a background flags for this But if a bot ignores you then it’s down to who ever runs it to shutdown there unethical waste of energy.