Nobody in the UK would care about that, unless your Jewish/Muslim or Vegan/Vegetarian.
As for the number of vegetarians and vegans, the UK reports 11% who live at least vegetarian or stricter per [1].
Unfortunately I haven't been able to find vegetarianism and religion correlations for the UK, but in any case it's safe to assume that anything between 11 and 19% of the UK's population are in one way or another following ethics that refuse gelatine-based products. That is not "nobody" at all.
[1] https://www.food.gov.uk/sites/default/files/media/document/f...
A more useful study "puts the size of the vegan population at about 2-3% and the vegetarian population at about 5-7%" [1].
From the article, it appears that only 2% of vegans, and 3% of vegetarians surveyed did so for religious reasons.
[1] https://yougov.co.uk/topics/lifestyle/articles-reports/2022/...
That doesn't even come close to being a safe assumption; it's wildly overoptimistic.
Kind of like claiming that, since Buddhists are forbidden to kill insects, and almost everyone in Thailand is Buddhist, killing insects is rare in Thailand.
We already know that most vegetarians are happy to eat meat. Compare https://academic.oup.com/ajcn/article/78/3/626S/4690004 , finding that two out of three self-described vegetarians had eaten meat within the past one day. They are even less likely to be worried about incidental animal products in candy.