Cannot adjust ProductPrice in "simple" theme

[anatomie]

I'm trying to add VAT to the visible price of products in my theme, e.g. exerpt from product-template.liquid:

            <span id="ProductPrice" class="product-single__price" itemprop="price" content="{{ current_variant.price| times:1.2 | divided_by: 100.00 }}">
              {{ current_variant.price | times:1.2 | money }}
            </span>

It's not working, as some Javascript (I assume) is overwriting this element after the page loads. Does anybody know how to do properly?

PS: Shopify is not currently a viable solution for UK sellers who want to sell internationally, due to this issue.