This what the law says:
“What the law says on Delivery Charges and Delivery Restrictions
You must indicate clearly no later than at the beginning of the ordering process if any delivery restrictions such as geographical restrictions apply
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You should not offer ‘Free or Standard Delivery’ to the ‘UK’ or to ‘Mainland UK’ if you don’t offer this to every relevant postcode.
You must tell your customers if there are any delivery charges and what they are as soon as reasonably possible in the ordering process. You must tell them before the contract is agreed.
Information on delivery charges should be easy to find on your website and easy to understand.
If information about delivery charges is not provided, or if it’s difficult to understand, then the customer may not have to pay delivery charges.”