Hi,
So I don't think that the problem is that the system uses the billing address.
However, I see two potential problems:
- You're using the "Europe" zone. Make sure that the UK is not in the list of sub zones of that Europe zone via the menu System>Zones. Otherwise, that tax rule will be valid for users in the UK.
- Your second tax rule is for another tax category. So if your products are all linked to the "default VAT" tax category, that tax rule will never apply.
Besides that, it seems ok.
If you really see the tax change when you change the billing address and not change when you change the shipping address, then I don't see how that's possible. Please double check and if you're able to reproduce the issue, please provide a link to the shop and precise instructions to reproduce the issue.