Duty charges in the UK work a little bit differently than they do in the Caribbean.
When you have shipped something to the UK, you will be contacted by the Royal Mail or your Courier who will instruct you on how to pay for your goods. Normally, customers are given about three weeks to make payments before the items are turned back.
If your parcel is coming from outside the European Union or is above a certain value, you could be charged for VAT (Value Added Tax).
In order for your Import Duty tax to be calculated, you must know the HS (Harmonised System) code for your parcel.
Orders under £135 are exempt from duty charges.
Gifts between £135-£630 are charged a duty rate of 2.5% of the total cost.
For gifts above £630 and any other goods above £135, the duty rate varies. It is in these cases, that the HS code is essential for calculating the duty charge.
For an item to be considered a gift, it must be declared as a gift on the customs form and the parcel must be sent between two people (not companies) and should be for an appropriate occasion such as a birthday or Christmas.
References:
https://wise.com/gb/import-duty/