There’s only a dozen threads with similar issues. 🤣
The courier in the UK will normally collect duties on behalf of the govt.
There are standard codes for tariff rates that you can look up online, so knowing what is in the package you can look up what the duty rate should be. This is also helpful if you want to query of challenge the tariff rate applied to your package.
There will also be a handling fee charged by the courier for this service, which tends to be £8+. The courier will get in touch and says “you have a parcel with duty to be paid. pay us ££££££ and we will deliver your parcel”